34 MONOCOTYLEDONS^. 



The structure of the grasses is extremely simple ; 

 consisting of fibrous roots issuing from a flattened 

 crown or collet, whence spring hollow or solid jointed 

 stems linear leaves borne on the joints of the stem, 

 which latter bear a terminal spike or panicle of per- 

 fect or phsenogamous flowers and seed. 



In duration they are either annual, as Hordeum 

 vulgar e ; biennial, as Bromus tectorum; or perennial, 

 as Dactylus glomevata. Some are minute herbs, 

 forming a thick turf ; others are arborescent, rising 

 to the height of many feet ; mostly stoloniferous, 

 by which they are increased as well as by seed. 



The physical structure, vital powers, and manner 

 of development, may be described as follows, viz : 



The seed is covered by a husk of cellular tissue, 

 inclosing a farinaceous albumen which contains the 

 corculum or embryo plant. The embryo, as in all 

 other cases, is composed of two principles, viz. the 

 rostellum from which the radicle fibres are exserted, 

 and the plumula, which rises in the air. Both proceed 

 from the base of the seed ; the first leaf hourly in- 

 creasing in height, and succeeded by others evolved 

 from within it ; in fact the first leaf evolves all the 

 others, together with the stem and fructification. 



Botanists are not agreed which member of the 

 infant plant is the true cotyledon. At the base of 

 each stem there is a small scale-like substance called 

 the vitellus, and immediately above this there is a 

 delicate sheath embracing the incipient leaves and 

 stem, and through which they come forth. The latter 



