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Botany 115 Terminology
Flower Terminology Part 2
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Go To Flower Terminology
Part 1 |
7. Shapes Of Flowers
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Left: Pacific madrone (Arbutus
menziesii), an evergreen tree with smooth red bark that is native to
forests of the Pacific coast of North America. It occurs in isolated
(disjunct) populations in the mountains of southern California and northern
Baja California. Arbutus peninsularis is endemic to mountains of the
Cape region in Baja California. Another Mexican madroņo (A. xalapensis)
grows in mountainous regions of Sinaloa and Chihuahua south through Veracruz
and Oaxaca to Guatemala. Right: The urn-shaped (urceolate) flowers of the
European strawberry tree (A. unedo) are typical of madrones, manzanita
(Arctostaphylos) and other members of the heath family (Ericaceae).
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8. Shapes Of Flowers (Cont.)
Papilionaceous Flower Of Fabaceae (Legume Family)
Family Fabaceae--Subfamily Papilionoideae:
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A dissected flower of Erythrina
crista-galli showing all the major perianth segments removed from their
attachment inside the calyx. The five petals consist of one large, oval
banner or standard, two elongate keel petals that are fused together
enclosing the stamens, and two reduced wings. Nine stamen filaments are
united into a sheath that surrounds the pistil. One stamen filament is
separate from the fused nine, a condition referred to as diadelphous. A drop
of nectar is secreted at the base of the petals inside the calyx. At maturity
the banner is widely separated from the keel petals, thus making the nectar
fluid at the base of the petals (within the calyx) readily available to
short-billed perching birds. Erythrina species pollinated by
hummingbirds have elongate, tubular blossoms. In true papilionaceous flowers (subfamily Papilionoideae), the upper petal is outside the lateral petals in the bud. This subfamily includes most members of the Fabaceae, including Dalea (smoke tree), Lupinus (lupine), Lathyrus (sweet pea), Erythrina (coral tree), Robinia (black locust) and Astragalus (locoweed). |
Family Fabaceae--Subfamily Caesalpinioideae:
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Members of the subfamily
Caesalpinioideae have flowers that are bilateral, typically with five
distinct petals, upper petal (banner) enveloped in the bud by the lateral
wings. This subfamily includes Cassia (senna), Cercis (redbud),
Bauhinia (orchid tree), Cercidium (palo verde), Parkinsonia
(Jerusalem thorn), Caesalpinia (brazilwood), Haematoxylum
(logwood), Ceratonia (carob), Tamarindus (tamarind) and Delonix
(royal poinciana). |
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The orchid tree (Bauhinia
variegata) native to India and China. The beautiful blossom superficially
resembles an orchid. Although it is truly a legume, it is not papilionaceous.
The upper petal is enveloped in the bud by the lateral wings. |
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A. Jerusalem thorn or
Mexican palo verde (Parkinsonia aculeata), a tree native to deserts of
Arizona and Baja California. B. Brazilwood (Caesalpinia echinata), a
tree native to Brazil and one of the important dyewoods of the 1600s. The
flowers are bilateral (irregular) but not truly papilionaceous. |
Family Fabaceae--Subfamily Mimosoideae:
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Red powder puff (Calliandra
haematocephala) native to Bolivia. Members of the subfamily Mimosoideae
have flowers with radial symmetry, small, inconspicuous corollas and
numerous, showy stamens. The flowers are typically in many-flowered heads or
spikes. This subfamily includes Acacia (wattle), Albizia (silk
tree), Samanea (monkeypod), Prosopis (mesquite) and Calliandra
(powder puff). |
Myrtaceae: Eucalyptus
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The bisexual flowers of Eucalyptus
polyanthemos showing the cylindrical cap (operculum) that separates to
expose a mass of white stamens which surround the female pistil. The majority
of flowering plant species have fewer than 20 stamens. |
9. Flower Symmetry
10. Ovary Position
11. Placentation
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Cross section of the
ripened ovary (fruit ) of a bell pepper (Capsicum annuum) showing
three locules (chambers) and axile placentation. The central region where the
seeds are attached is the placenta. In hot chile peppers, the placental
region contains up to 89 percent of the alkaloid capsaicin. This alkaloid
causes a burning sensation when it comes in contact with the sense receptors
in your tongue. Capsaicin is produced by a dominant gene. Since bell peppers
are homozygous recessive for this trait, they do not produce capsaicin.
Depending on the cultivar, green bell peppers ripen into bright shades of
yellow, orange and red. |
12. Typical Flower Of The Grass Family (Poaceae)
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In herbaceous (nonwoody)
grasses, such as wheat, rice, barley and oats, each leaf has a basal sheath
that envelops the grass stem (culm) down to its point of origin (node). At
the upper end of each culm sheath is the actual leaf blade, which typically
extends away from the culm. At the junction of the sheath and blade is a
small, membranous scale called the ligule. Minute projections at the base of
the leaf blade are called auricles. Grass leaves grow from an intercalary
meristem at the base of the sheath in the node region. This is why the
tranversely cut blades of grass plants in your lawn grow upwardly, even
though you mowed them off the previous week. The meristematic region of
herbaceous annual and perennial grasses is at the base of the leaves and
continually produces more leaf tissue. This is undoubtedly an adaptation to
grazing animals which could destroy the grass plant if the vulnerable growth regions
were apical rather than basal. Flowering (seed-bearing) stems of cereal
grasses develop from apical meristems that generally do not resprout if the
peduncle (flower stalk) is severed. Annual grasses (including many weedy
grasses in San Diego County) die following their blooming cycle. Perennial
grases die back to the rhizome and resprout the following year. The structure
and growth of bamboo leaves is very different from herbaceous grasses. It is
explained in the Wayne's Word article about bamboo. |
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Annual blugrass (Poa
annua), a common naturalized weed in southern California. The leaf blade
extends down the culm as an enveloping sheath to a slightly enlarged point of
attachment on the culm called the node. The internodes of grass stems are
typically hollow. In fact, hollow bamboo culms have many uses, including
blowguns, flutes and the transport of water. At the junction of the leaf
blade and culm sheath is a small scalelike ligule. The floret consists of two
bracts called the palea and lemma. Within the floret is the apetalous,
bisexual grass flower consisting of a gynoecium (pistil) and three stamens
(androecium). Following pollination and fertilization, the ovary develops
into a one-seeded fruit called a grain or caryopsis. In some grasses, the
minute remnants of perianth segments called lodicules are visible at the base
of the ovary. Grasses are typically wind-pollinated, although some species
have cleistogamous, self-pollinated flowers that remain closed within the
bracts of the floret. Note: A rather obscure characteristric used in the Jepson Manual key to grasses is the term "callus." This is a slight thickening (enlargement) at the connection point (junction) between the lemma and the main axis (rachilla) of a spikelet. In the naturalized Poa annua the callus is glabrous, while in the native P. bolanderi the callus is pubescent with cobwebby hair. This requires very careful examination. Although the callus of P. annua is glabrous, the base of the lemma has cobwebby pubescence. |
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Littleseed muhly (Muhlenbergia
microsperma), showing a cleistogamous spikelet at the base of a lower
leaf sheath. Several self-pollinated spikelets may be contained within a
tightly-rolled leaf sheath, which readily disarticulates from the plant at
maturity. The grains from these cleistogamous spikelets are larger than
grains from the terminal spikelets. This species is a native, clumping,
annual grass in dry areas of coastal sage scrub and creosote bush scrub in
southern California. |
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Littleseed muhly (Muhlenbergia
microsperma). A basal leaf sheath has been split apart to expose two
cleistogamous spikelets. These are fertile, self-pollinated spikelets that
are completely contained within the tightly-rolled leaf sheath. |
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Deergrass (Muhlenbergia
rigens) in a grassy meadow of the Cuyamaca Mountains, San Diego County.
This native perennial bunchgrass is relatively common in canyons and mountain
meadows of southern California. It was widely used by the Cahuilla people for
making baskets. |
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General structure of a
coiled basket. Bundles of flowering stems (culms) of deergrass (Muhlenbergia
rigens) were commonly used by the Cahuilla and other tribes for the
foundation (primary coils) of the basket, around which the secondary coils
were tightly wrapped. Basketbush (Rhus trilobata) was commonly used
for the secondary coils, with intricate designs made from brown coils of rush
culms (including Juncus acutus, J. effusus, J. lesueurii
and J. textilis). Sometimes the rush culms were dyed to produce
various color patterns. Other plants were also used for basketry in the
American southwest, including willow (Salix), beargrass (Nolina
microcarpa), yucca (Yucca elata) and devil's claws (Proboscidea
parviflora). |
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The Mysterious
Flowering Cycle Of Bamboo |
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Plantlets (bulblets) of Poa
bulbosa, a perennial bluegrass with florets that develop into small
bulblets while still attached to the inflorescence. This species is
propagated by bulblets rather than ungerminated grains. It was intoduced from
Europe and has spread throughout the northern United States and mountainous
regions of California. |
13. Grasses, Sedges and Rushes Compared
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Plants of the sedge family
(Cyperaceae) and rush family (Juncaceae) superficially resemble grasses;
however, they are quite different from true grasses. Like grasses, they have
small flowers without colorful petals; however, they do not have many of the
unique floral characteristics of grasses, such as the palea, lemma, glume and
grain (caryopsis). The ovary of sedges develops into an achene, while the
ovary of a rush (Juncus) develops into a many-seeded capsule. Like
grasses, sedges and rushes are important grazing plants for herbivorous
animals and provide valuable nesting sites in wetland habitats. Sedge and
rush stems often contain spongy aerenchyma tissue with abundant air spaces.
This allows air to reach the root systems which are often submersed in
water-logged mud. Rush stems (Juncaceae) are generally circular in cross
section, while the stems of sedges (Cyperaceae) are typically three-sided
(triangular). A few species in the Cyperaceae are used by people. The fibrous
stems of papyrus (Cyperus papyrus) are an ancient source in paper
dating back more than 5,000 years, and the crispy corms of water chestnut (Eleocharis
dulcis) are an important component in many Asian entrees. |
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A comparison of the typical
flowers of the grass family (Poaceae), sedge family (Cyperaceae) & rush
family (Juncaceae). In grasses, the individual flower is referred to as a
floret. In the sedge family, each flower is subtended by a scalelike bract.
Since the scalelike petals and sepals of the rush family are very similar in
appearance, they are referred to as tepals. The ovary of a grass develops
into a one-seeded grain (caryopsis). The ovary of a sedge develops into
one-seeded achene, while the ovary of a rush develops into a many-seeded
capsule. |
