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The Rosids are a large group of diverse eudicots that, together with Asterids, Caryophyllids, and a few other lineages, make up what are known as the "crown eudicots". Morphological characteristics that unite the Rosids as a monophyletic group are scarce; the current widely accepted view of subclass Rosidae includes many flowering plants once included in the former Dilleniidae and Hamamelidae by traditional taxonomists. Most Rosids have flower parts in multiples of 4 or 5, but some are wind pollinated, catkin-producing plants with miniscule flowers. Families that possess fused sepals or a receptacle elongated into a hypanthium are common in the Rosids.
Purple denotes orders containing families covered in class; green denotes orders photographically represented but not covered in Biology 414. Click on the tree to skip directly to a given order.
Rosid families covered in class: Geraniales: Geraniaceae (Geranium Family) Myrtales: Onagraceae (Evening Primrose Family) Oxalidales: Oxalidaceae (Wood Sorrel Family) Malpighiales: Euphorbiaceae (Spurge Family) Salicaceae (Willow Family) Fabales: Fabaceae (Legume Family) Cucurbitales: Cucurbitaceae (Cucumber Family) Fagales: Betulaceae (Birch Family) Fagaceae (Beech Family) Juglandaceae (Walnut Family) Rosales: Rosaceae (Rose Family) Urticaceae (Nettle Family) Brassicales: Brassicaceae (Mustard Family) Malvales: Malvaceae (Mallow Family) Sapindales: Aceraceae (Maple Family)
Staphylea trifoliata Bladdernut- Bladdernut grows in wet areas, such as streamsides. Its name comes from the papery, hollow capsules containing nut-like seeds.
Order: Geraniales *Geraniaceae: (Geranium Family) Identification characteristics: Geraniaceae have basal, alternate, or opposite, stipulate leaves that are usually lobed, indented, or compound. The flowers are actinomorphic (in our range), have 5 sepals that are unfused, 5 distinct petals, 5 or 10 (usually) stamens, and 5 carpels that are fused into an elongated, beak-like ovary. The fruit is typically a schizocarp with a central axis in the ovary. 5 valves around the axis coil violently at maturity, catapulting the seeds for dispersal. Many Geraniaceae have fragrant herbage when touched. Interesting stuff: Mitochondrial genes accumulate few mutations in most angiosperms, but members of Geraniaceae have apparent mutation rates much faster than other plants, sometimes over 10 times faster. Members of the genus Pelargonium are the "Geraniums" of garden fame and are zygomorphic with a spurred sepal, traits not found elsewhere in the family. Other genera are often used as ornamentals as well, sold under the name "storksbills" or "cranesbills." A member of the family is also often sold as a "mosquito plant," its citronella-like fragrance supposedly helping to ward off insects. Geranium maculatum Wild Geranium- In the same family as the garden geranium, this perennial is sometimes called Cranesbill due to its elongated fruit. Geranium maculatum Wild Geranium (closeup)- The flowers of Wild Geranium can range from very pale pink to dark purple. Geranium maculatum Wild Geranium (fruit)- The five valves of this Geranium schizocarp have already catapulted the seeds for dispersal.
Decodon verticillatus Water Willow- From a distance, this native species highly resembles the related, invasive Purple Loostrife. Decodon is shrubby and often has whorled leaves. Rhexia mariana Pale Meadow Beauty- The flowers of Rhexia open early in the morning, and the petals often fall off by mid-day. It is native to S.E. PA and the S.E. U.S. *Onagraceae: (Evening Primrose Family) Identification characteristics: Flowers of Onagraceae may be actinomorphic (see Oenothera) to zygomorphic (see Gaura), but usually have 4 sepals fused into a hypanthium tube, 4 distinct petals, 8 stamens, and 4 carpels included in an inferior ovary that usually matures into a capsule. The stigma is often 4-branched, forming a distinctive cross-like structure. The pollen is associated with viscous threads that help it to stick to pollinators. The flowers of Circaea, commonly encountered in PA, are reduced to 2 sepals, petals, and stamens. Interesting stuff: Numerous studies molecular studies have been done on Oenothera and other members of the family, including work on their unusual chloroplast genomes. Some, including many Fuchsia, are commonly grown as ornamentals. Gaura biennis Biennial Guara- The flower color in this species ranges from pink to white. The flowers open early in the morning and are short-lived. Oenothera biennis Evening Primrose- As its name suggests, Evening Primrose flowers usually only open near dusk, when they are pollinated by moths.
Celastrus scandens American Bittersweet- American Bittersweet may be declining due to competition from the introduced, weedy Oriental Bittersweet.
*Oxalidaceae: (Wood Sorrel Family) Identification characteristics: Leaves of Oxalidaceae may be in a basal rosette but are usually alternate. In our range, all have trifoliate leaves, but these may be palmately or pinnately compound in other regions. The flowers are radially symmetric and heterostylous (see discussion under Asterids: Rubiaceae). Populations may have two forms of flowers (distyly) or three forms (tristyly). There are 5 separate sepals, 5 distinct petals, and ten stamens which are connate for a length at their bases. There are usually two different lengths of stamens within a given flower. The 5 carpels are fused into a superior ovary that is often beak-like at maturity. It usually forms a capsule with seeds that are surrounded by a turgid aril which springs open rapidly, dispersing the seeds a distance from the parent plant. Interesting stuff: Oxalidaceae are named for the presence of oxalic acid in their tissues. Many species of Oxalis are common lawn and garden weeds that are sometimes chewed and referred to as "sour-grass." Probably the most economically important member of the family is Averrhoa carambola, the fruit of which is often sold as "star-fruit." Oxalis acetosella Northern Wood Sorrel- This plant of cool woods has larger flowers than some of its yellow-flowered, lawn-weed relatives.
Hypericum mitchellianum Mt. Mitchell St. John's-Wort- Native only to the highest elevations in the S. Appalachians, this species is abundant at the top of Mt. Mitchell, NC. *Euphorbiaceae: (Spurge Family) Identification characteristics: This family is difficult to characterize, as they are vegetatively and florally variable. Flowers are unisexual (sometimes appearing bisexual; read about cyathium, below). They often, but not always, have milky sap, they may have opposite or alternate leaves, and they may or may not have stipules. Euphorbia inflorescences are highly modified and highly variable. They are usually surrounded by bracts, which may be colorful for pollinator attraction (such as the red bracteal leaves of Pointsettias) or have colorful appendages that appear as the petals. The individual flowers themselves are usually minute. In plants with individually recognizable flowers, there are usually a few sepals (often 4) which are variably fused and 3 to 20 stamens in male flowers. Female flowers have three carpels fused into one ovary. The three styles are often subdivided or fringed. The flowers of many Euphorbiaceae in our range may not be readily individually recognizable. In these, the bracts often form a cuplike structure known as a cyathium (pl. cyathia) which may have a number of glands along its perimeter that resemble petals (the whole appearing as a hypanthium with a number of distinct petals). Inside the cyathium are one to many male flowers, each of which often consists of a single stamen. There is generally only one female flower inside a cyathium, and it is usually pedicellate (a good clue that you are looking at a flower inside of a cyathium; ovaries usually aren't long-stalked inside a flower). Cyathia may include all male flowers, only female flowers, or a mixture of both. Interesting stuff: Many Euphorbiaceae are highly toxic when ingested. Some may have stinging hairs reminiscent of Urticaceae. Rubber trees (Hevea) are the major source of natural rubber, and some are cultivated for ornamental use (spurges, pointsettias, crown-of-thorns, etc.). Euphorbia coronata Crown-of-Thorns (not native)- The cyathia of this Euphorbia contain many small unisexual flowers. The red "petals" are cyathial glands. Identification characteristics: Salicaceae are woody shrubs and trees. The leaves are alternate, simple, variously serrated, and usually have stipules. The plants are dioecious. Male and female inflorescences are both produced in catkins. There is generally no perianth, and the flowers are mainly wind-pollinated, although some willows produce nectar and fragrance that attract insects. Stamens vary in number in the male flowers. There are 2 to 4 connate carpels in the superior ovary of female flowers.The fruits form a capsule, the seeds released from which possess a tuft of hairs at their base that aid in wind dispersal. Interesting stuff: Salicaceae are sometimes used for their wood but are more often used for their pulp. Many are fast growing and are commonly used in paper-making. Many are planted ornamentally and as fast-growing wind-breaks or shade trees. The bark and stems of some Salix (willow) were once chewed medicinally, as they contain salicylic acid (aspirin). Hybanthus concolor Green Violet- The sturdy habit, flower shape, and color of this plant somewhat disguise its affinities to members of the genus Viola. Viola palmata Palmate Violet- Palmate Violet leaves are lobed variously deep, but never as deeply as V. pedata. V. palmata is found in dry woods. Viola pedata Birdsfoot Violet- Birdsfoot Violet has distinctive dissected leaves. It usually grows in inhospitable dry sandy soils and rock crevices. Viola pubescens Downy Yellow Violet- This species comes in a glabrous variety that was once separated as a distinct species, the Smooth Yellow Violet. Viola rostrata Long-Spurred Violet- Although all violets have a small spur on their lowermost petal, Long-Spurred Violet spurs are over half an inch long. Viola rostrata X striata Long-Spurred/Cream Violet Hybrid- Members of the genus Viola commonly form hybrid swarm populations. Viola sagittata var. ovata Ovate-Leaved Violet- The length of the pubescent leaf blades exceeds the length of the petioles in this violet . Viola sororia Early Blue Violet- Viola sororia and relatives are a taxonomically difficult group, and are commonly lumped into one species. Viola striata Cream Violet- Cream Violet usually has white rather than cream-colored flowers. The leafy stems with toothed stipules help aid identification.
Identification characteristics: A feature that characterizes all Fabaceae is their fruit, a legume or derivative thereof. Some Fabaceae may have constrictions in the legume between the seeds (the fruit then being called a lomentum), with each seed dehiscing separately. Most Fabaceae also have alternate, stipulate, compound leaves, which are most often pinnately compound or trifoliate. They may be trees, shrubs, or vines. Floral structure is variable in the family as currently monophyletically recognized, although they generally all have a gamosepalous calyx that forms a hypanthium. In the group formerly separated as Mimosaceae, the 5 petals are generally fused and the corolla is actinomorphic. In this mimosoid clade, there are usually numerous stamens per flower. In the group formerly separated as Caesalpiniaceae, flowers may be actinomorphic (see Gymnocladus below) or zygomorphic (see Cercis). There are ten stamens in this group, which may or may not be monodelphous. Often, one is a sterile staminode. In zygomorphic caesalpinioid and faboid (a.k.a. papilionoid) flowers, the flower shape is referred to as papilionaceous (meaning butterfly-like). These flowers have an upper petal called a banner that is generally enlarged, two lateral petals called wings, and two petals that form a boat-like structure known as the keel surrounding the reproductive organs. Caesalpinoid flowers usually have the banner as the innermost petal in bud, and thus the wings appear to be inserted behind it in the open flower (see Cercis). In faboid legumes, the wings appear to be in front of the banner, which seems to be the outermost petal (see Desmodium glutinosum). Faboid legumes usually have diadelphous stamens, with one stamen separate and the other 9 fused together. The keel petals of papilionaceous types may be connate, connivent, or easily separable. Interesting stuff: Fabaceae are famous for their nitrogen-fixing capabilities. The roots possess nodules which contain bacteria (such as Rhizobium) capable of fixing atmospheric nitrogen to forms biologically usable to plants. For this reason, Fabaceous species are particularly important to habitats with low soil nitrogen, such as recently burned areas or overused cropland. Fabaceae is the third largest family of angiosperms (behind Asteraceae and Orchidaceae). Legumes are one of the most agriculturally important angiosperm families, with beans, peas, peanuts, and lentils being just a few of the food plants in the family, and alfalfa and clover are just two of many that are grown as animal forage. They are very important in crop rotation systems for replacing lost soil nutrients. Many, such as Honey Locust (Gleditsia), Redbud (Cercis), Lupines (Lupinus), amd Wisteria, just to name a few, are grown as ornamentals. Trees such as Black Locust (Robinia pseudoacacia) may also be grown for timber. A widely accepted alternate name for Fabaceae is Leguminosae. Note: Caesalpiniaceae, Mimosaceae, and Fabaceae are listed as separate families in your manual. Amphicarpa bracteata Hog Peanut- The annual vines of Hog Peanut climb and trail, often forming a groundcover in woods and edges that regrows from seed each year. Baptisia tinctoria Yellow False-Indigo- This Baptisia forms a shrub-like mass that teams with insect life, paticularly once the flowers begin to bloom. Desmodium cuspidatum Big Tick-Trefoil- This species can grow to 2 meters tall in dry woods and thickets. Desmodium glutinosum Sticky Tick-Trefoil- This is probably the most common Desmodium in woods across PA. The lomentum disperses as separate seed compartments. Lathyrus latifolius Everlasting Pea- (Non-native) This perennial pea is found in a variety of colors from white to deep magenta. Lupinus perennis Wild Lupine- Wild Lupine likes sandy soil and can tolerate frequent burns in its habitat. Lupinus perennis Wild Lupine- The racemes of Lupines are indeterminant, meaning they can continue to elongate and produce new flower buds indefinitely. Lupinus perennis Wild Lupine- The taproot of Wild Lupine can extend to a depth well over a meter below the soil surface. Lupinus perennis Wild Lupine- Bumblebees usually forage from bottom to top, forcing their way into each flower "keel" where nectar and pollen may be found. Lupinus perennis Wild Lupine (legumes)- The legumes of Wild Lupine contain a number of small, hard seeds that must be abraded before they will germinate. Robinia pseudoacacia Black Locust- Black Locust wood was a popular fencepost wood, as it can last in the ground for 50 years or more without rotting. Cercis canadensis Redbud- Redbud is a widely planted ornamental small tree, but reaches the northernmost edge of its native range here in PA. Cercis canadensis Redbud- Notice the wings seem to insert behind the banner petal, a trait used to group "Caesalpinioids." Gymnocladus dioica Kentucky Coffee Tree- This tree is functionally dioecious, the male inflorescences generally having more flowers than this female. Polygala paucifolia Fringed Polygala- This plant is sometimes called Flowering Wintergreen. The flowers are sometimes likened to "Purple Elephants." Polygala paucifolia Fringed Polygala- The fringes are extensions of the middle petal of this flower used to entice pollinators. Polygala senega Seneca Snakeroot- This plant produces many more, albeit much tinier, flowers than its relative, Fringed Polygala.
*Cucurbitaceae: (Cucumber Family) Identification characteristics: Cucurbitaceae are almost invariably twining vines with alternate leaves and coiling tendrils at the nodes. The nodes originate at a 90 degree angle from the leaf stalks. The flowers are almost always unisexual, the plants often being monoecious and sometimes dioecious. Flowers are usually 5-merous (6) with the calyx fused and forming a hypanthium. Petals are fused, as are the stamens, which are sometimes individually unrecognizable. There are generally 3 carpels, although each stigma may be 2-lobed, thus giving a 6-carpellate appearance. Fruits are often berries (called a pepo when the rind is tough) but sometimes may be dry and capsular at maturity. Interesting stuff: The gynoecium of many Cucurbitaceae strongly resembles the androecium, presumeably tricking insects visiting the flowers to consume pollen into accidentally visit both types of flowers. Cucurbitaceae provide many agriculturally important crops, such as melons, squash, cucumbers, and pumpkins. Echinocystis lobata Wild Cucumber- Wild Cucumber is an annual vine, but it can reach high into trees by the end of its single season of growth. Echinocystis lobata Wild Cucumber- Only a couple of female flowers are produced per inflorescence. They are generally found at the base of the panicle. Echinocystis lobata Wild Cucumber (fruit)- The fruit of Wild Cucumber isn't Cucumber-like at all. It is a dry, spiny capsule with a few large seeds at maturity.
Identification characteristics: Betulaceae have alternate, stipulate, simple leaves that are variously serrated and pinnately veined. They are all monoecious shrubs or trees with the male and female flowers borne in catkins. The plants are wind-pollinated and bloom in early spring before the leaves fully emerge. Male catkins are pendulous, with each bracteal scale subtending 2 or sometimes 3 flowers each usually with 4 stamens, although the flowers are often so small and crowded that the individual flowers may be indistinguishable. The tepals, variable in number, are minute. Female catkins may be drooping and be similar in appearance to the male catkins, or they may be erect and cone-like, with the bracteal scales hardening to the texture of gymnosperm cones. The ovary of female flowers is inferior and comprised of 2 carpels (2 style branches). The seeds are often associated with adnate secondary and tertiary bracts which may aid in wind dispersal of the seeds of some species. The single-seeded fruits may be classified as nuts, achenes, or samaras. Interesting stuff: Betulaceae provide many ornamental trees and some products useful to humans, such as filberts and hazelnuts (Corylus), and birch beer and birch bark canoes (Betula). Many Alnus species have nodules on their roots that serve as homes to nitrogen-fixing, symbiotic bacteria. This allows them to colonize nitrogen-poor soils (such as bogs, burned over areas, volcanoes, etc.) rapidly, and they may be important transition species in those environments. Alnus incana Speckled Alder (male and female catkins)- At maturity, the female catkins of alders form cones reminiscent of gymnosperms. Alnus serrulata Smooth Alder (male and female infl. and fruits)- The wind-pollinated flowers of Alders bloom before the leaves are produced. Alnus serrulata Smooth Alder (female inflorescence)- The bracts of these female inflorescences will enlarge and harden to form "cones." Carpinus caroliniana American Hornbeam, Ironwood- This tree is also sometimes called musclewood because of its sinewy, smooth bark. Corylus americana American Hazelnut (male catkins)- The flowers in the catkins of Hazelnut are among the earliest blooming in spring. Corylus americana American Hazelnut- The female inflorescence is usually produced at the branch tip, while the catkins are at least one node back. Corylus americana American Hazelnut (female inflorescence)- Although multiple female flowers are produced in the inflorescence, only one will produce a nut. Identification characteristics: Fagaceae have alternate, simple leaves that are pinnately veined and stipulate. The plants may be shrub-like, but are most often large trees at maturity. Like other members of the order Fagales, Fagaceae are monoecious and have inconspicuous flowers that are almost always wind-pollinated. The male flowers are usually borne in elongated catkins, but they may be more densely clustered in a globose array. Each male flower has 4 to numerous stamens. The female flowers are always surrounded or subtended by a group of spiny or scaly bracts known as a cupule that may take various forms (the cap of an acorn or the hull of a beechnut or chestnut). There are 3 inferior carpels fused into one ovary, each with 2 ovules, but only one per ovary reaches maturity. Interesting stuff: Fagaceae are major constituents of temperate, northern hemisphere forests of the old and new world. Economically, many are sometimes planted as street or shade trees, but they are of major importance as timber trees. Acorns and beechnuts were once a major source of food for Native Americans, and they are a major food source for many forms of wildlife in eastern North America. Chestnuts are still a commercially important product of Fagaceae, although the American Chestnut (Castanea dentata), once a dominant tree of ridges in PA and elsewhere in eastern North America, has been decimated by the introduced fungus known as chestnut blight (Cryphonectria parasitica). Cork is made from the bark of an oak (Quercus) species. Many trunks of beech trees (Fagus) are permanently defaced by inconsiderate people who carve their names in the smooth gray bark, ruining the natural beauty of the tree for others. Quercus macrocarpa Bur Oak (male catkins)- The male flowers of Oaks are borne in catkins that arise from the junction of new growth with the previous year's growth. Quercus macrocarpa Bur Oak (female flowers)- The female flowers are produced inconspicuously in the axils of new growth, but will form large acorns with frilled caps. *Juglandaceae: (Walnut Family) Identification characteristics: Juglandaceae have alternate, pinnately compound leaves that have no stipules. They are usually trees at maturity, and have wind-pollinated, inconspicuous flowers. There may be 3 to many stamens per male flower, which are borne in elongate, drooping catkins. The plants are monoecious, with the female flowers produced in one to few-flowered aggregations that are nearly sessile. The 2 carpels form an inferior ovary that is surrounded by bracts which are generally adnate at maturity. The fruit is a nut (such as hickory nuts) that may have a separable husk, or a drupe (as in walnut), where the husk is somewhat fibrous and surrounds an inner pit. Interesting stuff: Juglandaceae are valuable timber trees and provide edible fruits, such as pecan (Carya illinoensis), other hickory nuts (Carya), and walnuts (Juglans). The roots, rotting leaves, and rotting husks of some Juglans species release chemicals that stunt or kill other plant species growing nearby (a phenomenon known as allelopathy). This helps keep competition from other trees down as the walnut trees become established. The nuts of Juglandaceae are primarily rodent-dispersed, although some hickory nuts may be bird-dispersed.\ Carya cordiformis Bitternut Hickory- The catkins of hickories usually mature later than oaks; the hickory leaves are usually almost fully grown at flowering. Carya cordiformis Bitternut Hickory- Like oaks, the male catkins of hickories are produced on growth from the previous year. Comptonia peregrina Sweet Fern- The catkins of Sweet Fern bloom before the fern-like, pleasant-scented leaves appear.
Ceonothus americanus New Jersey Tea- New Jersey Tea is sometimes called Redroot. The straggling shrubs are often found on wooded slopes. Ceonothus americanus New Jersey Tea- This shrub prefers moist slopes with lots of Calcium, and is usually found near limestone. Identification characteristics: Rosaceae may be herbs, shrubs, or trees. They generally have alternate, toothed, stipulate leaves that may be simple or compound. The flowers have 5 sepals fused into a hypanthium, the flowers thus being perigynous when the ovaries are superior. Sometimes, the carpel or carpels may be fused to the hypanthium, forming an inferior ovary. There are 5 distinct petals which often taper to a thin stalk (claw). The stamens are generally numerous, distinct from each other on the hypanthium. There can be one to many carpels, and the fruits are variable. Numerous, separate achenes may be dispersed within a fleshy swollen hypanthium (e.g. rose hips), a single pit may form within a fleshy drupe (e.g. cherry), the separate carpels may be dispersed together as an aggregation of drupelets (e.g. raspberries), or the separate carpels may form achenes that are dispersed together with a fleshy floral receptacle (e.g. strawberry). Other fruit types in the family include follicles and a specialized berry known as a pome (apples, pears, etc). Interesting stuff: Black Cherry (Prunus serotina) is one of the most valuable woods. Numerous economically important fruits are found within Rosaceae, such as apple (Malus), pear (Pyrus), cherries, plums, peaches, almonds, and apricots (Prunus), blackberries and raspberries (Rubus), and strawberries (Fragaria). Some of the many ornamentals in the family include crab apples, spiraeas, flowering cherries, and, of course, roses. Amelanchier arborea Downy Serviceberry- The flowers on this serviceberry open in early spring before the leaves have expanded. Amelanchier stolonifera Low Juneberry- Species of Amelanchier acquire the name "Juneberry" because their early flowers produce ripe fruit before most other fruiting trees. Amelanchier stolonifera Low Juneberry- The leaves of this species are about half-grown when the flowers open. Aronia melanocarpa Black Chokeberry- Black Chokeberry is usually found in sphagnum bogs in PA. The anthers are bright pink when fresh. Dalibarda repens Running Violet- This plant is only distantly related to true violets and has white flowers, but the leaves strongly resemble them. Fillipendula rubra Queen-of-the-Prairie- This beautiful plant can be found in wet meadows in PA, but is more common in midwestern prairie states. Fillipendula rubra Queen-of-the-Prairie- Not surprisingly, this and other species of Fillipendula are often grown as ornamentals. Fragaria virginiana Wild Strawberry- This plant is one of the parents of the cultivated strawberry, but its smaller fruits, although more tart, are very good. Physocarpus opulifolius Ninebark- This shrub gets its name from the stripes of bark (which may number less or more than 9) that run down its stems Porteranthus trifoliatus (Gillenia trifoliatus) Bowman's Root- Also known as Mountain Indian Physic, this plant can form large clumps. Potentilla canadensis Canada Cinquefoil- Cinquefoils are sometimes called "Five-Fingers" due to their palmately compound leaves. Prunus serotina Black Cherry- Black Cherry is one of the most valuable hardwoods in the world. It is a much more common in PA than it was historically. Prunus virginiana Chokecherry- Chokecherry grows as a small shrub, usually near forest edges. The fruits, although popular with birds, are very bitter. Rubus odoratus Flowering Raspberry- Although the most beautiful of our native raspberries in flower, the fruit of this species is dry and not sweet. Sorbus americana American Mountain Ash (in fruit)- This species is found at progressively higher elevations the further south one travels in the Appalachians. Spiraea alba Meadowsweet- Meadowsweet grows in wet sunny areas, often forming dense stands on the outskirts of sphagnum bogs. Ulmus americana American Elm- The dangling, inconspicous flowers of American Elm are wind-pollinated early in spring before leaves emerge. Ulmus americana American Elm- American Elm populations were devestated by Dutch Elm Disease in the 20th century. Cannabis sativa Hemp, Marijuana- (Non-native) In addition to use as a medicinal drug, Cannabis has long been cultivated for its oil, seeds, and particularly for its valuable fiber. The highly glandular female inflorescences of marijuana are rich in THC, the compound responsible for the psychoactive effects of this plant. Cannabis sativa Hemp, Marijuana- Each female flower has two styles extending from the ovary, which will form an achene at maturity if pollinated. Note the glandularity. Identification characteristics: Urticaceae are best known known for the painful sensation experienced when one makes contact with hairs on the plants' surfaces, but not all species in the family are capable of stinging. The plants may have opposite or alternate leaves that are generally stipulate. The flowers are usually unisexual (plants may be monoecious or dioecious) and are individually inconspicuous and tiny. They are borne in axillary clusters (sometimes a terminal cluster is also present). There are usually 4 (occasionally 5) sepals that may be slightly fused. Male flowers have 4 or 5 stamens, and female flowers have one style on top of the superior ovary, which eventually forms an achene. Interesting stuff: The stinging hairs of many species easily penetrate skin and release acetylcholine and histamine which cause painful tingling, and itching sensations. Stinging nettles are actually edible if properly boiled. The leaves of Urticaceae serve as host plants for many Nymphalid butterflies, such as commas, question marks, and red admirals (they don't have to boil the leaves first). Laportea canadensis Wood Nettle- Wood Nettle is less potent than its relative Stinging Nettle (Urtica), but still produces some of the same stinging hairs. Pilea pumilla Clearweed- Unlike many other Urticaceae, this species has no stinging hairs. It often densely covers the ground in moist areas.
*Brassicaceae: (Mustard Family) Identification characteristics: Mustards normally have alternate leaves that may be simple, deeply divided, or compound. The major leaves are often in a basal rosette. Flowers are generally in racemes that often lack any remnants of bracts subtending the flowers. Floral formula of the family as traditionally recognized, is very distinctive. The calyx is comprised of 4 distinct sepals. The 4 petals are also distinct and usually clawed (with a thin stalk expanding into a blade). There are 6 distinct stamens which are usually recognizably tetradynamous (4 long and 2 shorter). The superior ovary is two-carpellate and forms a two chambered capsule-like fruit with a persistent central divider known as a replum. Fruits that are slender and elongate, often flattened parallel to the replum, are known as siliques. Some fruits may be flattened perpendicular to the replum, forming a fatter fruit-type known as a silicle. Interesting stuff: Brassicaceae produce chemicals known as glucosinolates which are the active ingredients in mustard oil and mustard gas and which impart distinctive flavors to edible members of the family. Selective breeding in the single species, Brassica oleracea, has given rise to such agriculturally important crops as brocolli, cabbage, kale, cauliflower, kohlrabi, and brussels sprouts. Turnips, mustard, radish, horse radish, and canola oil are also important food products of the family. A few species are grown ornamentally, and many species are very weedy, including the allelopathic Alliaria petiolata (garlic mustard), which is rapidly invading woodland habitats of the eastern U.S. to the detriment of native wildflower species. Arabidopsis thaliana is the most studied vascular plant for molecular and developmental biology due to its short generation time, ease of cultivation, and small genome size. It is the first plant to have its entire genome sequenced. The family was formerly known as Cruciferae, a name still commonly encountered in old books and herbaria. Cardamine concatenata (Dentaria laciniata) Cut-Leaved Toothwort- This early spring wildflower grows in moist woodlands. Cardamine concatenata (Dentaria laciniata) Cut-Leaved Toothwort- Toothworts die back early in the summer after dropping seeds.
Identification characteristics: Malvaceae have alternate, simple, stipulate leaves that are palmately veined and sometimes palmately lobed. The flowers are often surrounded by a whorl of bracts. The 5 sepals are valvate and are generally fused for a portion of their length. The 5 petals are usually distinct and showy. There are usually numerous stamens which are variably syngenesious, most often forming a monodelphous tube surrounding the gynoecioum. There are usually 5 styles or stigmas that are exerted from this androecial tube. The 5 carpels are fused into a single superior ovary that usually matures into a 5-locular capsule. Interesting stuff: Malvaceae provide many ornamental flowers and shrubs, along with a number of economically important products such as okra (Hibiscus esculentus) and cotton (Gossypium). Some taxonomists now combine Sterculiaceae, which includes the plant responsible for chocolate (Theobroma cacao), with Malvaceae. Hibiscus palustris Swamp Rose-Mallow- The flowers of Swamp Rose-Mallow come in two very distinct forms: white with crimson centers (pictured) or entirely pink. Hibiscus palustris Swamp Rose-Mallow- The numerous stamens are syngenesious, forming a tube around the style. The 5 distinct stigmas indicate the 5 carpels. Hibiscus palustris Swamp Rose-Mallow- The whorl of thin bracts around the calyx of Hibiscus are known as the epicalyx. The calyx is valvate, while the petals are convolute in bud. Tilia americana Basswood, American Linden- The fruits are dispersed, in part, by the wing-like bract adnate to the inflorescence stalk.
Identification characteristics: Members of this family are usually small to large trees with opposite leaves that may be simple and palmately lobed to pinnately compound. The flowers are usually functionally unisexual, although vestigal organs of the other sex are often found in flowers of either type. The flowers usually have 5 tepals, but that number is variable. Stamens are variable in number but usually around 5. Female flowers are 2-carpellate, with a single superior ovary that is 2-lobed with 2 separate styles. The fruit is a schizocarp (referred to as a double samara), which splits into 2 individually winged seeds that are blown by the wind in "helicopter" fashion. Interesting stuff: Molecular systematists have found close relationships between this family, Hippocastaneaceae, and Sapindaceae, and some now lump them together into the latter family. Maples are largely wind-pollinated, although their small flowers may be quite colorful when magnified. They bloom in spring, either before or while the leaves are expanding. Maples are an important component of eastern deciduous forests (as well as forests in other temperate regions) and are economically valued for their lumber and for maple syrup, which is usually produced from Acer saccharum, one of the most common trees in eastern North America. Acer negundo Box Elder (male inflorescence)- Box Elder is often also referred to as Ash-Leaved Maple due to the compound leaves, which are unusual for a maple. Acer negundo Box Elder (female inflorescence)- The female flowers of Box Elder give rise to double samara schizocarps typical of maples. Acer rubrum Red Maple (female inflorescence)- The staminodes found within female Red Maple flowers occasionally produce viable pollen. Acer rubrum Red Maple (female flower)- The female flowers of Red Maple each have 2 elongated styles for receiving wind-borne pollen. Acer rubrum Red Maple (male inflorescence)- Multiple flowers are found within each erupting bud, which are again clustered to form the inflorescence. Acer rubrum Red Maple (male flower)- The wind-pollinated flowers of Red Maple open early in spring before the leaves emerge. Acer rubrum Red Maple (ovary)- The two-lobed ovary will eventually mature into two separate, helicopter-like seeds. Acer saccharum Sugar Maple (infructescence and leaves)- The leaves of sugar maple are the most integral part of the foliar spectacle seen in autumn in the northeastern U.S. Acer saccharum Sugar Maple (mature ovary/seeds)- The ovary splits schizocarpically, and each of the two seeds disperse separately via wind. Acer spicatum Mountain Maple- Mountain maple produces erect spicate inflorescences. It is a small, understory tree. Rhus glabra Smooth Sumac- Smooth Sumac is a fairly common, thicket-forming shrub in PA. The leaves turn brilliant red in autumn. Rhus typhina Staghorn Sumac- Staghorn Sumac is distincguished from other Rhus by its dense pubescence on new stem growth. The berries can be used to make a lemony drink. Aesculus glabra Ohio Buckeye- The Buckeye seed is enclosed by a spiny husk in this species, whose seeds are rich in bitter tannins. Aesculus glabra Ohio Buckeye- Ohio Buckeye is the state tree of. . .Ohio! The seeds were sometimes used by Native Americans to poison fish. Aesculus pavia Red Buckeye (Native to S.E. U.S.)- Red Buckeye usually grows on sandy coastal plain soils, where it blooms as hummingbirds are migrating north. Zanthoxylum americanum (male inflorescence)- Prickly Ash is dioecious, with separate male and female trees. It is more closely related to Orange trees than to true Ash trees. Zanthoxylum americanum (male inflorescence)- Paired stipular spines are present at many of the nodes of Prickly Ash. Zanthoxylum americanum (female inflorescence)- The number of carpels within the flowers of Prickly Ash vary from 3-5; the flowers are apocarpous. |
