VIIl] 



FRUITS OF GRASSES 



123 



Thirdly, the outermost layer or layers of cells of the 

 endosperm are filled with proteids, and are known as 

 the Aleurone layer. (Fig. 38, A.) 



The embryo consists of the folded embryonic leaves in 

 bud (plumule) above, which will grow up on germination 

 as the shoot or " spear," the short primary root (radicle) 

 below, with in many cases two or more secondary rootlets 

 already showing in its tissues, and 

 from the common "collar" uniting il 



these a more or less prominent 

 shield -shaped organ (scutellum) 

 standing out laterally in contact 

 with the endosperm, the dissolved 

 contents of which it absorbs on 

 germination. (Fig. 38, s.) 



Although typical grasses form a 

 caryopsis as described, exceptions 

 occur. In the exotic Sporoholus, 

 Eleusine, Grypsis and Heleochloa the 

 fruit becomes truly dehiscent, the 

 seed being loose in the fruit, and the 

 latter opens and allows it to fall out ; 

 and in many Bamboos the seed is 

 loose in the achene, while in a few 

 cases — e.g. Melocanna— the fruit is 

 fleshy and may be as big as a 

 walnut. 



Eeturning to the typical grasses. 

 When the fruit ripens in the spikelet, several events may 

 happen. 



Fig. 40. 

 bens. 

 size : 



a 



Triodia decum- 



a, "seed," nat. 



b, ditto, X 6. 

 Note the basal hair- 

 tuft and raohilla, and 

 the ciliate, toothed 

 outer palea with a 

 short awn-point, en- 

 closing the inner more 

 delicate palea. Be- 

 tween the two lies the 

 caryopsis. Nobbe. 



