12 THE AGRICULTURAL GRASSES OF THE UNITED STATES. 

 GENERAL DESCRIPTION OF GRASSES. 



A grass possesses the followiug parts : (1) the root, (2) the culm, 

 (3) the leaves, (4) the flowers. 



(1.) The roots are the fibrous ramiticatious which extend downward 

 into the ground and appropriate the water or other liquid nutriment to 

 be convej'ed into the stem and leaves. 



(2.) (The stem or culm is the ascending part which commonly rises 

 above ground, either erect or reclining. Sometimes the €ulm is hori- 

 zontal and subterranean, sending out erect branches and fibrous roots 

 at the joints. These are called creeping stems, or, improperlj^, creeping 

 roots. They are botanically called rhizomes, and sometimes are sev- 

 eral feet long. In some grasses there is a kind of bulb at the base of 

 the stem, in which is stored a concentration of nutriment for the support 

 of the plant under peculiar circumstances, as in protracted drought. 

 This bulbous formation is a part of the stem, and not of the root. The 

 stem or culm of grasses is usually cylindrical and hollow ; sometimes it 

 is more or less compressed or flattened. It is divided at intervals by 

 transverse thickened i>ortions called joints or nodes, at which points 

 leaves and sometimes branches are given oft. These nodes tend also to 

 strengthen the stem. Stems are usually simple and unbranched, except 

 at the top, where they commonly divide into the more or less numerous 

 branches of the ijanicle or flowering part. But some stems give rise 

 from the side joints to leafy branches, which may, like the main stem, 

 produce smaller i^anicles at the top. 



(3.) The leaves take their origin at the nodes or joints in two 

 ranks — that is, they are placed alternately on opposite sides of the stem 

 at greater or less distances — thus, the first leaf will be on one side, the 

 second on the opposite side a little higher up, the third still higher and 

 directly over the first, the fourth over the second, and so on. The 

 leaves consist of three parts : (1) the sheath^ (2) the ligule, and (3) the 

 hlade. The sheath is that part which clasps the stem. It is generally 

 open on one side, as will be readily observed in the leaves of a corn- 

 stalk, but in some grasses the sheath is partly or even completely 

 closed together by the adhesion of the opposite edges. The sheath is 

 analogous to the stem or petiole of the leaves of many higher plants. 

 The Ugtde : At the i^oint where the blade of the leaf leaves the stem, at 

 the top of the sheath and on the inner side, there is usually a small, 

 thin, leaf like organ, called the ligule or tongue. This is sometimes half 

 an inch long, more commonly only two or three lines, and sometimes it 

 is almost absent or reduced to a short ring, but its length and size is 

 very constant in the same species. This ligule represents the stipules 

 which occur at the base of the leaves in many of the higher plants. 

 The hlade or lamina of the leaf is the expanded part which is commonly 

 called leaf. In the majority of grasses the leaf is long and narrow ; 

 that is, many times longer than wide. There is one central nerve, called 



