560 STRUCTURE OP SEED OF GRASSES. 



which is called an awn. Where the flowers are arranged in 

 spikelets, termed locustece, each of these has one or a pair of 

 glumes at its base by which it is more or less enclosed. Of all 

 these parts, the interior scales are the only ones which bear any 

 resemblance to the calyx or corolla of more perfect flowers ; the 

 remainder are to be considered as bracts. 



735. If the ovary be cut across, nothing but a kind of pulp 

 will be found within it ; this substance then fills the young 

 ovule, which entirely occupies the cavity of the ovarium ; and 

 its own envelopes and the walls of the ovarium grow together, 

 in such a manner as to be scarcely distinguishable. When 

 ripened, however, the ovary, becomes hard ; and its own walls 

 and the membranes of the seed having coalesced still more 

 closely, all trace of the originally distinct seed-vessel is lost. 

 Such a seed, which appears destitute of an external casing, but 

 which has really been developed within one, is properly termed a 

 grain (see . 504). The great mass of the seed consists of the 

 separate albumen ; and the embryo 

 itself is very minute, and not easily dis- 

 covered by an unpractised Botanist. If 

 the grain be laid upon its flat face, so 

 that the convex side is uppermost, a 

 minute oval depression will be seen 

 towards the narrowest end ; and if the 

 seed- coat be carefully removed, a littlo 

 oval body will be found lying half em- 



Fio. 201. SBKD OF GRASS J 



A, external view, showing a, bedded in the albumen. If this be 

 divided Perpendicularly with a sharp 



showing the plumula a, the k n if e ft W JU |, e f oun d to Consist of a 

 radicle 6, and the cotyledon ..,.,?, , , . , . .. . . 

 the whole embryo being on the thlCKlsh Scale, which IS the Single COty- 

 outeide of the albumen d. ledon . ^ up(m ^ j.^ ft j.^ ^.^j 



body, composed of several minute sheaths fitted one over the 

 other, which is the plumula ; whilst at the opposite extremity 

 will be found the radicle, or rudiment of the root. When the 

 radicle first begins to grow, the cotyledon swells a little, and 

 attaches itself firmly, by the whole of its absorbent surface, to 

 the albumen ; and this, as it is gradually changed in the process 



