6 THE GRASSES OF MAINE. 



ground stems, unlike the true roots, have joints with scales repre- 

 senting the leaves, and from these joints rootlets are put out and 

 new plants developed. 



The stems of the grasses consist of nodes and internodes, or joints 

 and the spaces between them. The joints are solid, and a cross 

 section is circular in all our species with the exception of wire grass 

 (Poa compressa, L., plate XVII) . In this species the node or 

 joint is compressed or flattened so that it cannot be rolled between 

 the thumb and finger. The internodes, or spaces between the joints, 

 are hollow in all the Maine grasses except corn and a grass found 

 growing occasionally on our sea beaches and known as Beach grass 

 (Ammopliila arundmacea, Host.). 



The arrangement of the leaves on the stem is of great importance 

 in distinguishing the grasses from some of the related families of 

 plants. In the grasses there is one leaf from each node or joint, 

 the first from the lowest joint of the stem ; the second from the next 

 joint above, but on the opposite side of the stem ; the third leaf from 

 the third joint and on the opposite side from the last leaf, but directly 

 over the first, and so on. The leaf consists of the sheath (petiole), 

 the liyule and the blade (lamina) . The sheath is the part surround- 

 ing the stem, and which, starting up from a node, extends nearly up 

 to the next node, where it joins the long, narrow blade of the leaf. 

 Although the sheath surrounds the stem, the edges merely touch or 

 overlap, but are never grown together except in exceedingly rare 

 cases. At the place where the sheath ends and the blade begins, 

 there is a thin and more or less transparent membrane called the 

 ligule. This is an upward continuation of the sheath above its 

 junction with the blade of the leaf, and, as it varies in size and form, 

 it is much used in the classification of the grasses. The blade is 

 long and narrow, with a stout vein through the middle called the 

 midrib, and smaller veins on each side parallel to the midrib. 



The flowers of the grasses are variously arranged in panicles (for 

 an illustration of a panicle see plate IX or plate XIX) or spikes 

 (see plates I and II), each individual flower consisting of what are 

 called the essential organs and the protecting organs, which simply 

 enclose and protect the essential organs. These last consist of 

 stamens and SL pistil, which may both occur in the same flower, when 

 it is said to be perfect, or one flower may contain only the stamens 

 and another only the pistil. Flowers in the former case are said to 

 be staminate or sterile, in the latter, pistillate or fertile. When the 



