20 



THE TRUE GRASSES. 



ally consists merely of a few cell layers ; one, a very 

 thick-walled epidermis, and several of tolerably tliin- 

 walled parenchyma with delicate fibro- vascular bundles, 

 and an inner epidermis that is frequently indistinct. It 

 contains no amylaceous material, and when the grain is 

 ground it, together with the adjacent layer of albumen, is 

 removed as bran. In many grasses the pericarp unites 

 more or less with the bracts, growing especially to the 

 palea, seldom to the flowering glume. Those caryopses 

 adherent to the bracts (e.g., most barleys) must not be 

 confused with those in which the bracts are close around 

 the fruit but not grown to it (for example, in Spelt, Tri- 

 ticum spelt a L., whose fruit is often spoken of as ad- 

 herent). After long soaking in water the bract may 

 with care be removed even from the adherent fruit. 



The following fruit forms are more rare in grasses : 

 Utricle — the pericarp thin, dehiscent, free from and sur- 

 rounding the seed ; for example, Sporobolus (Fig. 51, l\ , 

 Jc 2 ), Eleusine (Fig. 71, k), Grypsis, and Heleochloa ; Nut- 

 fruits in some Bambusere (Dendrocalamus, Pseruhistn- 

 chyum, Schizostachyum, etc.) and in Zizaniopsis ; Berries, 

 often as large as apples, as in the Barnbuseaz, Melocala- 

 mus, Melocanna, and Ochlandra. The berries of Melo- 

 canna bambusoides are often from 8 to 13 centimeters in 

 diameter and are edible. 



Upon the caryopsis is a place where the embryo lies 

 covered only by the pericarp 

 and plainly visible on the out- 

 side (Fig. 6, B). This place is 

 upon the front side (that is, the 

 side facing the floral glume) of 

 the base of the fruit. Opposite 

 to it, or on the posterior side, 

 the fruit bears a more or less 

 clear, sometimes punctiform 

 and sometimes elongated or 

 linear mark, the hilum, the place where the seed was 

 fastened to the wall of the ovary (Fig. 5). 



Since the form of the hilum is constant in every 

 genus, and also sometimes in whole tribes, it is very im- 



Fig. 5.— A, Fruit of Agrostis sesqui- 

 flora, Desv., with punctiform hi- 

 lum; B. of Pennisetum Chilense, 

 with an oval-bordered one; C, of 

 Bromus Mango Desv., with a 

 linear hilum. (After Desvaux 

 Gram, and Cyp. Chil.) 



