GKAMIXE/E 587 



spikelet it drops off; it rarely protrudes from the glume 

 or falls separately. The pericarp is usually very thin, closely 

 adnate to the seed with a mark over the hilum, rarely 

 loose, membranous, or in some members of the tribe Bam- 

 buseas, hard and crustaceous or very thick and fleshy. The 

 seed-coat is adnate to, and not to be distinguished from the 

 pericarp, or is free from the latter and very thin and adnate 

 to the endosperm. The endosperm is copious, and farinaceous 

 or rarely fleshy. The embryo is small, globose or depressed, 

 often minute and situated at the base of the endosperm. It 

 shows a very characteristic distinction of parts, and often a 

 high development. The most characteristic is the cotyledon, 

 which consists of two clearly separated portions : the scutellum 

 or absorbent organ which remains in the seed in germination, 

 first causing the solution of the nutrient endosperm and then 

 absorbing it ; and the sheathing portion which protects the 

 plumule and in germination penetrates the soil and appears 

 above the earth still enveloping the first green leaf. This view 

 of the morphology of the cotyledon was hinted at by Gaertner l 

 and subsequently elaborated and strongly insisted on by Van 

 Tieghem 2 from the anatomy of the organs especially the course 

 of the vascular bundles. A similar arrangement has lately 

 been described by Tschirch in the Scitarninese (see ante, p. 566). 

 The radicle is enclosed in the root-sheath (coleorhiza) ; several 

 lateral rootlets are often indicated. 



Seedling. The germination of Grasses has been carefully 

 investigated by many workers from Mirbel, Poiteau and Eichard 

 onwards. It differs from that of Cyperaceaa by the radicle, and 

 not the cotyledon, first emerging and growing rapidly down- 

 wards. The root-sheath is first slightly protruded from the 

 seed, but is soon broken by the root which rapidly elongates, 

 and is usually closely covered with hairs, which are also often 

 found on the free surface of the root-sheath. The cotyledonary 

 sheath grows upwards, penetrates the testa, pericarp, and the 

 glume when present, and makes its way through the soil as 

 a sharp wedge, while the scutellum slowly absorbs the endo- 



1 De Fructibus, &c. 1788, i. p. cxlix. 



2 ' Observations anatomiques sur le Cotyledon des Graminees,' Ann. Sci. 

 Nat. ser. v. torn. xv. (1892), p. 236. 



