Distribution: Widespread
in all climates and regions. Grasslands made up of species in
the Poaceae make up 20% of the world's vegetational cover.
Economic Uses: The most
important plant family to humans, the Poaceae is the source of
all the cereal crops cultivated throughout the world, such as;
wheat, rice, maize (corn), oats, barley, millet, rye, sugar cane
and sorghum. The grasses are also significant as grazing crops
and some larger ornamentals. As building materials and a source
for matting, the bamboos are highly valued in Asia.
Defining
Features of Interest: The Poaceae (or
Gramineae), has been classified by characters of the spikelet,
but this has changed at present to a focus on different micro
and macro anatomical features, so the arrangement within the family
is still somewhat undefined. The distinctive floral anatomy results
in a specialized terminology.
Fossil Evidence: Fossil
pollen from the upper Cretaceous and fossil pollen and grains
from the Paleocene and Eocene.
Floral Features : Zygomorphic and perfect or unisexual/ monoecious or dioecious. Perianth may be lacking. Inflorescence is of spikelets which are then arranged into panicles, racemes or spikes. Each spikelet is subtended by 2 (or 0-7) glumes (or bractlets). The florets (flowers) are each enclosed by two bractlets termed the lemma and palea. The bractlets sometimes produce a stiff bristle termed an awn. If a floret has a perianth, it is modfied as two fleshy lodicules.
Fruit and Seed Features : Fruit is a caryopsis or grain with the lemma and palea persistent. Seeds are fused to teh pericarp and with endosperm present. Placentation is basal.
Vegetative Features
: Habit is as herbs or rarely woody shrubs or trees. Leaves are
simple, linear, narrow and alternate or basal in two ranks(or
rows). Bases are sheathed with open, overlapping margins. Auricles
and \or ligules are present where the stem, leaf blade and sheath
meet.
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