74 BOARD OF AGRICULTURE. 



mon and small centre into large patches ; as though they creep for 

 a considerable distance, yet their points ultimately rise to the sur- 

 face and then expand into new leaves, and in fact form distinct and 

 perfect individuals, which if separated from the parent, all the more 

 rapidly give rise to independent colonies, and indeed these scions do 

 as their parents did before them. Several species of grasses have 

 this tendency, and consequently when it occurs it forms a good dis- 

 tinctive character. Hence, though the Triticiim repens has a 

 rhizome, the T. canininn is furnished only with a fibrous root. 

 Some of the Poas, as Poa pratensis and P. compressa, have rhiz- 

 omes, while Poa annua and P. triviaUs are without any. Several 

 species of grass become useful from this very structure, in keeping 

 together banks of sea coast, canals and the like. 



Culm — stem. The stems of grasses are usually hollow and 

 rounded, (except in Poa compresa, in which the name has been giv- 

 en from its oval form as though it had been subjected to pressure.) 

 The stem is separated into long or short lengths called ^'oi?/ ^5, by 

 the intervention of nodes (knots) which are solid, and tend much 

 to strengthen the structure of the plant, to which end they will be 

 found to be closer at the base where the strain would be greatest on 

 account of these light plants swaying forward and backward in the 

 wind, and more remote upwards in the culm, from which are sus- 

 pended the newer and more active leaves. Stems vary in being 

 smooth, ribbed, armed with hairs which may be long or short, bristly 

 or doAvny. The nodes again, may be of a different color from the 

 culm, or like it may be smooth or armed in a similar manner. 

 The leaves consist of the following parts : 

 The sheath — j)etiole or leaf stalk of other plants ; 

 The ligule or tongue ; 

 The lamina — blade or flat part of the leaf. 

 The sheath is the footstalk of the leaf This takes its rise from 

 the nodes, one from each, arranged on alternate sides of the culm. 

 The whole length of the sheath, which is variable, is folded around 

 the culm, from which it can be loosened by unwinding, without 

 fracture, a circumstance which serves to distinguish the grasses from 

 the sedges, {Care.v,) as the sheath of the latter is a continuous tube 

 in which the solid and often triangular cUlm is inserted, not folded. 

 This is a distinctive character of great importance to observe, inas- 



