STRUCTURE, MORPHOLOGY, AND PHYSIOLOGY. 21 



portant in identification, and enables us to recognize the 

 kind of attachment of the ovulum to the carpel even in 

 the fruit. A punctiform or only short oblong hilum at 

 the base of the fruit indicates a narrow, and an elongated 

 linear hilum an extended, attachment. If there is a fur- 

 row in the fruit, then the hilum is always to be looked 

 for in this, and moreover invariably on the side of the 

 palea, which must first be shaved off in those fruits 

 where the pericarp is adherent to the bracts. 



The embryo is usually small, seldom more than half 

 as long as the fruit, straight, rarely slightly bent (Oryza |, 

 with the radicle turned downwards. Its most striking 

 portion is the scutellum (Sc in Fig. 6), which is regarded 

 (although not undisputedly) as the cotyledon. It is a 

 fiat but somewhat thick body, roundish to elongated- 

 oval in circumference, lying close on its inner side to 

 the albumen, with the plumule and radicle surrounded 

 by the coleorhiza situated in its somewhat shallow ex- 

 terior. The plumule lies free upon the scutellum, but 

 below the plumule the axis of the embryo is united with 

 it ; this is the point of insertion of the scutellum beyond 

 which it projects downwards and outwards as far as the 

 point of the coleorhiza (Fig. 6, E, H). This descending 

 portion of the scutellum is grown for a longer (Wheat) or 

 shorter (Maize) distance to the jDosterior part of the cole- 

 orhiza, and its edges are either free at both sides (Triti- 

 cum, etc.), or they turn forward and grow so completely 

 over the coleorhiza that they entirely unite in front or 

 leave only a small cleft (Maize, L in Fig. 6, 31, Sorghum). 

 If this is the case, it is only in germination that the side 

 portions are pushed back (Fig. 6, N) and the entire 

 embryo becomes visible. The inside of the scutellum 

 shows a peculiar kind of epidermis, the so-called cylinder 

 epithelium, of palisade-formed, cylindrical cells with 

 delicate walls. They are for the purpose of absorbing 

 the dissolved amylaceous material of the albumen. The 

 scutellum also contains a fibro-vascular bundle, and this 

 often has short branches. In germination it remains 

 within the pericarp. 



In many grasses there is in front of the embryo and 



