124 



DISARTICULATION OF "SEED 



[CH. 



-P' 



In most of our grasses the caryopsis comes away 

 trapped between its two palea;, and the latter bring away 

 with them the small piece of the axis of the ^mkelet on 

 which they stand : this bit of axis — the rachilla — often 

 affords valuable characters in 

 diagnosis. (Fig. 41.) It is the 

 pair of paleae enclosing their 

 caryopsLs which goes by the 

 name of " seed " in most of our 

 grasses. (Fig. 40.) 



In a few cases, however, e.g. 

 Panicum, the spikelet comes 

 away as a whole, so that here 

 the " seed " consists of the 

 glumes, enclosing one, two or 

 more pairs of paleae with their 

 contained caryopses. 



Even among our native 

 grasses, however, cases occur 

 where the separation takes 

 place below some of the 

 glumes, and so the " seed," as 

 met with in samples, consists 

 of glumes as well as enclosed 

 palete and caryopsis — e.g. An- 

 thoxanthum, Alopecurus, &c. — 

 and some care is necessary in 

 examining grass " seed " in these circumstances (see p. 134). 



Interesting biological adaptations are met with in the 

 distribution of grass " seeds." The very small and light 



Fig. 41. Diagram of a spikelet 

 of a, grass — e.g. Festuca — 

 comprising six 'matured 

 flowers and their palese, 

 embraced by the two 

 glumes {g^g') at the mo- 

 ment of disarticulation as 

 the fruits ripen. The small 

 piece of axis (a) left attach- 

 ed to each segment is the 

 rachilla -R. At p^ the tip of 

 the inner palea is visible 

 protruding from the outer 

 one p^ : in the rest it is still 

 enclosed in the latter. 



