Grass, the most useful family of plants. There are more than
5,000 kinds of grasses. Some grow only about one inch (2.5 cm)
high while othersthe bamboosreach 100 feet (30 m) or more. They
grow in ordinary soil, in or near water, in deserts, and even in
Arctic wastelands. Many provide humans and animals with a large
part of their food needs. Other grasses are grown for lawns.
Still others are used as soil-builders, to help control erosion,
or in making such products as paper, cloth, and perfumes. Many
grasses are simply weeds. Most grasses are annual or perennial
herbaceous plants, but the bamboos and a few other species have
woody stems. The culms, or stems, of grass are cylindrical and
jointed. The leaves grow singly on opposite sides of the stem.
Each leaf consists of two partsthe sheath and the blade. The
sheath, or base of the leaf, encircles the stem just above the
node, or joint. The spear-shaped, parallel-veined blade rises
from the sheath at a sharp angle. The root system of annual
grasses is a simple