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The Monocots have only one seedling leaf (cotyledon) and usually have scattered vascular bundles, parallel veined leaves, and flower parts borne in multiples of three. The Monocot lineage probably branched off from other angiosperms either after or somewhere among the basal angiosperm lineages. One should keep in mind that although we talk about things systematically "branching" off over evolutionary time, all plants- in fact, all organisms- that we see on earth today have been evolving for the same length of time. Thus there really are no "higher" or "lower" organisms, although basal-branching lineages do often retain more characteristics that are ancestral to the group. Monocots are the most economically important group of plants to humans today, containing all grain crops (corn, wheat, rice, oats, barley, etc.). Relationships between Monocot orders are very unresolved, even with all current molecular and morphological data. Particularly problematic are Liliales and orders with similar floral structure (see discussion under Liliaceae). Within Monocots, there are many interesting modifications to the angiosperm flower, from the highly reduced, wind-pollinated grasses and sedges, to the highly specialized and elaborate flowers seen in orchids. The genus Acorus is probably the sister group to all other Monocots, although its spadix inflorescence has caused many taxonomists to group it with Araceae in the past. Acorus produces ethereal oils and has the "primative" odor characteristic of basal angiosperms. Like the basal angiosperms, monocots produce monosulcate pollen.
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.
Monocot families covered in class: Alismatales: Araceae (Arum Family) "Liliales:" Iridaceae (Iris Family) Liliaceae (Lily Family) Orchidaceae (Orchid Family) Poales: Cyperaceae (Sedge Family) Juncaceae (Rush Family) Poaceae (Grass Family)
Sagittaria latifolia Common Arrowhead- This plant usually grows in standing water or saturated soil; note the arrow-shaped leaves. Sagittaria latifolia Common Arrowhead (a closer look)- These flowers are female. The roots of some arrowheads are sometimes eaten. Identification characteristics: The key feature for most Araceae is the inflorescence structure, which consists of a spathe and spadix. The spadix is a fleshy elongation of the inflorescence axis that bears numerous, tightly packed flowers over its surface or localized at its base. The spathe is a sheathing bracteal leaf that may subtend or completely surround the spadix. The spathe is often showy and used for pollinator attraction. Plants may have perfect flowers, but more often are monoecious, with male and female flowers on separate portions of the spadix, or dioecious. The flowers themselves are usually minute and are variable. There may be no tepals, or 4 to 6 if they are present. There may be 1 to 6 stamens per flower, and 1 to 4 carpels fused into a superior ovary (which may be imbedded in the spadix). The fruit is usually a berry. Interesting stuff: Duckweeds (Lemna, Wolffia, etc.), formerly segregated into their own family (Lemnaceae), have now been shown to be highly reduced Araceae, consisting of one floating leaf and microscopic inflorescences. In the genus Arisaema, younger or unhealthy plants produce male flowers and older, healthier plants produce female flowers. This is also usually correlated with the number of leaves a plant is able to produce (1 in males, 2 in females). A plant may switch back and forth from being male or female from year to year. Araceae possess calcium oxalate crystals in their tissue which can cause serious inflammation if parts of the plants are ingested. After boiling and decanting numerous times, however, many (such as taro) are edible and make up a significant portion of the diet in some cultures. Many Araceae are ornamentals, such as Calla Lilies (Zantedeschia), Philodendron, Spathiphyllum, and others. Arisaema draconitum Green Dragon- The leaves of Green Dragon usually have seven or more leaflets. They may be 5 feet or more in height under good conditions. Arisaema draconitum Green Dragon- Unlike that of Jack-in-the-Pulpit, the spadix of Green dragon is exerted from the spathe to guide pollinators into the inflorescence. Arisaema triphyllum Jack-in-the-Pulpit- The flowers, usually all male or all female, are found at the base of the spadix ("Jack"), surrounded by the spathe. Arisaema triphyllum Jack-in-the-Pulpit- The spathe and spadix of Jack-in-the-Pulpit show wide variation in the extent of pigmentation. Arisaema triphyllum Jack-in-the-Pulpit (fruit)- The berries of Jack-in-the-Pulpit each contain a few seeds. Although tasty to some animals, the berries aren't edible to humans. Symplocarpus foetidus Skunk Cabbage- Skunk Cabbage often blooms in late February in marshy area of PA before the leaves develop.
Dioscorea villosa Wild Yamroot- Although supermarket yams are actually sweet potatoes, tropical relatives of this species produce similar edible roots.
Order: Liliales (including Asparagales) Identification characteristics: Iridaceae are identifiable by their floral formula, which consists of 3 sepals and 3 petals (which may together appear as 6 tepals), three stamens, and three carpels which are fused into 1 inferior ovary. The three style branches of Iridaceae are often colorful and sometimes quite petalloid to aid in pollinator attraction. Flowers in our range are all actinomorphic. Interesting stuff: Iridaceae and Orchidaceae are now referred to an order known as Asparagales (see discussion under Liliaceae). Many Iridaceae are among the most popular garden ornamentals, such as Iris, Crocus, and Gladiolus. In the genus Iris, the sepals droop or are held horizontally and are known as "falls." The petals, called "standards" in Iris, are generally more erect and are sometimes a completely different color from the falls. Iris cristata Dwarf Crested Iris (plant)- Dwarf Crested Iris grows on wooded slopes in southern PA. It often forms dense colonies. Iris cristata Dwarf Crested Iris (flower)- The sepals, petals, and style branches all contribute to the floral presentation of Iris. Iris versicolor Blue Flag- Blue Flag is a wetland species with long, straplike leaves that usually are taller than the flowers, which only last about a day each. Sisyrinchium angustifolium Narrow-Leaved Blue-Eyed Grass- Although related to irises, the tepals of Sisyrinchium are all identical. Sisyrinchium montanum Blue-Eyed Grass- The sheathing involucral leaves, or spathes, of this species are very different lengths. Identification characteristics: As covered here, Liliaceae have 6 tepals (sometimes recognizable as 3 sepals and 3 petals). The tepals may be fused or unfused. There are 6 stamens and three carpels which are fused into an ovary that may be inferior or superior. The fruits are usually capsules or berries. Interesting stuff: Liliaceae, as cicumscribed herein, are certainly not a monophyletic group. They have been variously split based on morphology, with Amaryllidaceae including species with inferior ovaries and Agavaceae including many desert succulents. Although molecular evidence isn't very conclusive at this point, genera that have traditionally been placed in Liliaceae have been split into three orders: Asparagales (which includes Iridaceae and Orchidaceae as well), Dioscoreales, and Liliales. Because many of the newly segregated families aren't well supported monophyletic groups and because many morphological characters that distinguish the new families are much less than obvious (e.g. seed coat epidermal traits), most things with a 3-3-6-3 (or 6-3-3) floral formula are listed here as Liliaceae. Members of this artificial group are well known as many of the most famous ornamental plants; Tulips, Lilies, Daylilies, Yucca, Daffodils, and Hyacinths are just a few. Plants used as food or in beverages include agave, asparagus, onions, garlic, and chives. Many Liliaceae are also a major component of the spring and summer flora of eastern North America (such as Trilliums and Trout Lilies). Note: Liliaceae (superior ovaries) and Amaryllidaceae (inferior ovaries) are listed as separate families in your manual. Allium cernuum Nodding Wild Onion (plant)- This onion is common in a variety of habitats from barrens to grasslands and dry wooded slopes. Allium cernuum Nodding Wild Onion (umbel)- The flowers of Nodding Wild Onion can range in color from almost white to deep magenta/ purple. Camassia scilloides Wild Hyacinth- Wild Hyacinth is most commonly found growing in river floodplains of the midwestern U.S. Clintonia borealis Blue Bead Lily- The common name of this species refers to the shiny blue fruits that are produced by the plant in late summer. Erythronium albidum White Trout Lily- Unlike Yellow Trout Lilies, White Trout Lilies aren't colonial, relying on seeding to spread. Erythronium albidum White Trout Lily- The stigmas of E. albidum are recurved, unlike the appressed stigmas of E. americanum, which form a club. Erythronium americanum Trout Lily- Trout Lilies often don't flower in a given year, spreading instead by underground runners that send up one leaf. Erythronium americanum Trout Lily- The anthers and pollen of E. americanum are red at dehiscence, unlike E. albidum. Notice the pollen on the stigmas. Hemerocallis fulva Daylily- (Non-native) This species is sometimes wrongly advertised as "native daylily." Each flower only lasts a single day. Lilium canadense ssp. canadense Yellow Canada Lily- Both yellow and red forms of Canada Lily are found across PA. Lilium canadense ssp. editorum Red Canada Lily- Canada Lily is most often found on wooded slopes and swampy woods. Lilium philadelphicum Wood Lily (flower)- Wood Lily is found in sandy, acidic soils and can often be located in pine barrens. Lilium philadelphicum Wood Lily (plant)- The orange flowers of Wood Lily only last a couple days and are often pollinated by large butterflies. Lilium philadelphicum Wood Lily (two flowers)- Wood Lily is our only eastern native lily with flowers that face upwards. Maianthemum canadense Wild Lily of the Valley- Also known as Canada Mayflower, this species is unusual for Liliaceae in having 4 tepals. Medeola virginiana Indian Cucumber Root- The whorled leaves of this species are much more conspicuous than the nodding, greenish flowers. Medeola virginiana Indian Cucumber Root- This plant is colonial, and few individual stems of a colony will bloom in any given year. Polygonatum pubescens Solomon's Seal- The inconspicuous green flowers of Solomon's Seal dangle beneath the leaves, two per cluster in this species. Smilacina racemosa False Solomon's Seal- False Solomon's Seal is common in deciduous woods. It produces red berries in late summer. Smilacina racemosa False Solomon's Seal- This species is sometimes also known as Solomon's Plume. Smilacina stellata Starry False Solomon's Seal- This species is found in moist, sandy areas. The inflorescence is a raceme rather than a panicle. Trillium albidum Pacific White Toadshade- (Native to Pacific Coast from WA to CA) This Trillium is perhaps the largest overall species on average. Trillium cuneatum Whippoorwill Flower- (Native to S.E. United States) This species has attractive mottled leaves. It usually grows near limestone. Trillium erectum Purple Trillium- This is the most common Trillium across most of PA. It is also called Stinking Benjamin due to its fetid-scented flowers. Trillium erectum Purple Trillium- Typical flowers of this species range from purple-brown to red. Trillium erectum album Purple Trillium (white form)- This unscented white morph may be found amongst purple forms or in all white groups. Trillium erectum Purple Trillium (typical, yellowish variant, pink variant)- Reddish, pink, white, and yellowish forms of this species may occur within a single population. Trillium flexipes Bent Trillium- The pretty flowers of Bent Trillium are usually inconspicuously held beneath the leaves. Trillium flexipes Bent Trillium (purplish flower)- Many species of Trillium show variation in color, # of flower parts, and/or # of leaves. Trillium grandiflorum Large White Trillium- The showiest of our Trilliums, this species is common to the West but largely absent in central PA. Trillium grandiflorum Large White Trillium- Trilliums are slow to clump via rhizomes, but these flowers are surprisingly all from one huge individual! Trillium luteum Yellow Trillium- (Native to S.E. United States) Yellow Trillium has a mild, pleasant scent. It is usually found in calcium-rich soils. Trillium sessile Toadshade- Toadshade shows a lot of variation in the color of its sessile, erect petals and in the extent of leaf mottling. Trillium sessile Toadshade- Toadshade faintly smells of rotten meat, a ploy used to attract carrion fly pollinators. Trillium sulcatum Barksdale's Trillium (Native to S.E. United States)- This species differs from T. erectum with its recurved petals and sulcate sepals. Trillium sulcatum Barksdale's Trillium (Native to S.E. United States)- This dark-flowered individual is being visited by a couple of flies. Trillium undulatum Painted Trillium- Painted Trillium is only found in acidic soils, such as those near sphagnum bogs. Trillium undulatum Painted Trillium- The reddish "eyspot" of Painted Trillium creeps peripherally into the veins of the petals. Trillium undulatum Painted Trillium (closeup)- The petals of Painted Trillium are more delicate than other Trilliums, and the flowers are short-lived. Trillium undulatum Painted Trillium (deformed)- It isn't uncommon to find variation in Trilliums, such as this four-leaved, two-petaled individual. Uvularia grandiflora Large-Flowered Bellwort- This species, also known as Merrybells, forms large clumps, adding to the attractiveness of the plant. Uvularia perfoliata Perfoliate Bellwort- Perfoliate Bellwort has numerous orangish, granular growths inside the tepals. Uvularia sessilifolia Wild Oats- This Uvularia usually only has one flower per stalk, and the leaves are sessile rather than perfoliate. Identification characteristics: Orchids have some of the most modified floral organs of any angiosperm, and much diversity in form occurs within the family; however, in general, orchids are one of the easiest families of flowering plants to identify. The flowers are zygomorphic, usually very much so. There are 3 sepals and three petals, but their color and texture varies considerably, sometimes with 5 of the 6 appearing tepaloid. One of the petals known as the labellum, is highly elaborated and usually brightly colored and or patterned. The labellum sometimes has appendages, outgrowths, fringes, or it may be modified into a pouch-like stucture (see Cypripedium spp. below). Developmentally, the labellum is the top petal, but in most orchids, the flower is resupinate (the pedicel twisting 180 degrees before anthesis), making the labellum appear as the lowermost petal. The reproductive organs of orchids are highly modified compared to monocot relatives. The stamens are fused to each other and to the gynoecium, forming a structure called the column. In basal lineages of orchids there are two (or three) stamens that split from the column near its summit, each containing pastey globs of pollen. Most orchids have only one unrecognizable stamen on the column that produces a waxy mass of pollen (pollinium) with a sticky pad (viscidium) that allows the pollinium to stick to floral visitors. The pollinia are transfered as one package to a receptive stigmatic surface. Most orchids possess a sterile portion of their stigma as a cap, beak, or extension of the column known as the rostellum. All orchids have an inferior ovary derived from 3 carpels that forms many thousands of dust-like seeds. Interesting stuff: Most orchids are highly dependent on micorrhizal fungi that live inside the epidermis of their roots. Orchid seeds are tiny and lack nutritional resources needed for germination. Most seeds must be contacted by fungi, which nourish the growing embryo. Mycoparasitism (mycotrophy), a condition in which the orchid is nonphotosynthetic and provides nothing to its fungal symbiont in return for all of its nutrition, has probably arisen more than once within Orchidaceae. The elaborate pollination mechanisms within Orchidaceae have probably helped to create the diversity of species seen within the family. Although many are rare, there are more described species in this family than any other monocot family. It is second in size within angiosperms only to Asteraceae. Economically, aside from the numerous ornamentals grown in greenhouses, vanilla flavor comes from the seed capsules of the orchid Vanilla planiflora. Aplectrum hyemale Puttyroot (leaf)- Puttyroot sends up a single leaf in fall, which dies away before the plant blooms in May. Aplectrum hyemale Puttyroot (inflorescence with beetle herbivory)- Puttyroot is a threatened species in PA. The leafless stalk appears parasitic. Cypripedium acaule Pink Lady's Slipper (front view)- Pink Lady's Slipper is sometimes known as Moccasin Flower. White forms may be found. Cypripedium acaule Pink Lady's Slipper (side view)- Insects enter through the slit in the front of the pouch, but must leave through the top. Cypripedium acaule Pink Lady's Slipper- Although colorful, the flowers of Cypripedium offer no reward to insects, and thus often fail to be pollinated. Cypripedium acaule Pink Lady's Slipper (plants)- The seeds of Cypripedium must be contacted by Rhizoctonia fungus before they will germinate. Cypripedium acaule Pink Lady's Slipper (white morph)- The white form of Pink Lady's Slipper varies in relative abundance across the species' range. Cypripedium pubescens Yellow Lady's Slipper- This species prefers soils less acidic than C. acaule; it is typically found in rich, often calcareous, woods. Cypripedium pubescens Yellow Lady's Slipper- The capsules of Yellow Lady's Slipper contain large quantities of dust-like seeds. Cypripedium pubescens Yellow Lady's Slipper- Yellow Lady's Slipper lacks the slit in the front of its pouch like C. acaule. Insects enter through the hole in the top. Habenaria orbiculata Round-Leaved Rein Orchis- The glossy, circular leaves of this species lie flat on the ground. It grows in moist, acid woods. Habenaria orbiculata Round-Leaved Rein Orchis (flower)- The flowers of this orchid possess a long, backwards-projecting spur that holds nectar. Epipactis helleborine Hellebore Orchid- (Non-native) This introduced species is common in forests as well as in flower beds with rotting bark mulch. Listera cordata Heart-Leaved Twayblade- This rare orchid grows near sphagnum bogs in PA. The tiny, camouflaged flowers are easily overlooked. Orchis spectabilis Showy Orchis- The upper lip of this beautiful orchid can range from pale pink to dark purple. Orchis spectabilis Showy Orchis- The flowers possess a backwards-projecting spur that holds nectar for insect pollinators. Spiranthes cernua Nodding Lady's Tresses- This orchid is found in sunny, usually moist openings in sandy, acidic soils. Spiranthes cernua Nodding Lady's Tresses- Spiranthes gets its genus name from the spiraled arangement of the flowers along the inflorescence. Spiranthes cernua Nodding Lady's Tresses- S. cernua flowers are usually borne in approximately 4 vertical ranks on the inflorescence axis. Spiranthes cernua Nodding Lady's Tresses- The tubular flowers appear un-Orchid-like, but when spread, the perianth and reproductive parts are clearly those of an orchid. Spiranthes cernua Nodding Lady's Tresses- The inflorescence axis, ovary, and perianth of S. cernua all possess glandular hairs.
Identification characteristics: Cyperaceae usually have trigonous, solid stems, and the leaves are alternate in three ranks. The leaf sheaths are closed up to the point where the blade diverges from the stem. The flowers are borne in complex arrangements know as spikelets (different from grass spikelets, see below). Most genera of sedges have miniscule flowers, each subtended by a scale that conceals it. The flowers are sometimes bisexual, but the plants are often monoecious, with male flowers and female flowers being located in different portions of a spikelet or in separate spikelets entirely. The tepals may be completely absent, but are often represented by small scales, hairs or bristles. There are 1 to 3 stamens with the anther bases not appearing sagittate. The superior ovaries may have two or three style branches; those with 2 form lenticular (rounded) achenes, those with 3 form (trigonous), 3-angled achenes. Some genera (e.g. Carex) have a prophyll associated with the female flowers elaborated into a sac (perigynium) that surrounds the achene. Interesting stuff: Carex is the most species-rich genus in North America. The anthers and stigmas are usually exerted conspicuously from the scales that hide the florets, as most Cyperaceae are wind-pollinated. Sedges are of only minor importance to humans agrigulturally (Papyrus was a sedge used to make paper by ancient Egyptians), but they are an important ecological component of many sunny habitats, such as meadows, glades, and marshes. Carex lurida Sallow Sedge- The achenes of this sedge are surrounded by a papery sac (perigynum) like other members of the species-rich genus Carex. Carex pennsylvanica Pennsylvania Sedge- The bottoms of the spikes show white styles protruding, while stamens are produced from florets at the top. Identification characteristics: Rushes have round, solid stems and hold their leaves in 3 ranks as do Cyperaceae (when leaves are present). However, the sheath of most rushes is open for a portion of its length on the stem, unlike Cyperaceae. Many members of the family appear leafless, with a pointed stem that has an axillary inflorescence. These inflorescences are actually terminal, and the portion of the stem above them is a bracteal leaf. The flowers and fruits of rushes help distinguish them from sedges and grasses. They have 6 tepals, 6 stamens (occasionally 3), and three carpels fused into a superior ovary. The ovary, when mature in fruit, splits open as a septicidal capsule. Flowers of Juncaceae may be subtended by tiny bracts known as prophylls. Interesting stuff: Rushes often grow in wetlands and marsh, but some may be found in surprisingly dry habitats. They have little economical value to humans. Sedges and Rushes have sometimes been separated into their own order, Juncales. Luzula echinata Wood Rush- Wood Rushes may be told from other rushes by the presence of pubescence. Identification characteristics: Grasses usually have stems that are hollow between the nodes, leaves in 2 ranks, and a sheath that is overlapping but usually open (unfused) for most of its length. A projection or fringe of hairs known as a ligule is sometimes present at the top of the sheath at the junction of the blade; the presence and consistency of the ligule are often used as characters in keys. Grasses may be monoecious, dioecious, or have perfect flowers. The flowers are arranged in structures known as spikelets, which consist of one to many florets (flower+palea+lemma). A spikelet generally has a set of 2 bracts known as glumes, which closely subtend and often overlap with the florets. Each floret is composed of a bract-like structure known as the lemma, which subtends the flower, and the palea, which encloses the flower from the rachis (axis) side of the floret. Lemmas, paleas, and glumes may have elongated midveins known as awns. Tepals are generally absent, although they are often represented by miniscule structures known as lodicules which sometimes function to separate the lemma and palea at anthesis. There are usually 3 stamens which possess sagittate anthers, and 2 styles. The fruit formed from the superior ovary is a grain. How the fruit detatches from the plant is also important in grass keys. Some species disarticulate (break at a joint) below the glumes, thus dropping the entire spikelet for dispersal. Other species disarticulate somewhere above the glumes, leaving them behind on the plant. Multiple florets may be dispersed together in this manner, or disarticulation may occur between each individual floret. Interesting stuff: Grasses exert their reproductive structures from the floret at anthesis and are wind-pollinated, often to the dismay of people with allergies. Aside from providing most of the world's caloric intake via grains such as rice, wheat, corn, barley, etc. and other food crops such as sugarcane, grasses are also used ornamentally, and, of course, as lawns and turf. They are also a major component of many ecosystems such as prairie, savannah, glades, and wetlands. Many photosynthesize via a mechanism known as C4. Unlike CAM plants (see Cactaceae), C4 grasses temporally rather than spatially separate their photosynthetic reactions. The open their stomata at night to let in carbon dioxide when water loss will be minimal. The carbon dioxide is then stored in 4-carbon compounds until day, when the stomata close and the carbon dioxide can be released and used in conjunction with light reactions. Bouteloua curtipendula Side-Oats Grama- Side-Oats Gramma is now a threatened species in PA, with only about a dozen populations left on limestone prairies. Bouteloua curtipendula Side-Oats Grama- The white, feathery stigmas and reddish, sagittate anthers are exerted from the spikelets to facilitate wind-pollination. Bromus kalmii Prairie Brome- Prairie Brome is another rare grass in PA, often found in the same limestone prairies where Bouteloua curtipendula dominates. Elymus hystrix Bottlebrush Grass- Bottlebrush Grass isn't clump forming, and is found in the un-grasslike habitat of rich woodlands. Sparganium americanum Bur Reed- Bur Reed grows in wet areas, often partially submerged.
Commelina virginiana Virginia Dayflower- This native species has much larger flowers and a more colorful lower petal than its introduced relatives. Pontederia cordata Pickerelweed- Pickerelweed grows as an emergent aquatic near the shores of ponds, marshes, and other stagnant waterways. Pontederia cordata Pickerelweed- Although not commonly found in central PA, Pickerelweed is very common in marshes in the eastern and western parts of the state. |
