80 



GRASSES OF IOWA. 



rhiza. This descending point of the scutellum is grown for a^ 

 longer or shorter distance to the posterior part of the co'eo- 

 rhiza, so that they entirely unite in front or leave only a small 

 cleft. If this is the case it is only in germination that the &ide 

 portions are pushed back and the em ire embryo becomes 

 visible." 



The scutellum has a most 

 interesting epidermal layer, 

 the so calU d cylinder epi- 

 thelium. These palisade- 

 like cylindrical cells are thin 

 walled and physiologically 

 of great importance to the 

 germinating plant. It is 

 the function of these cells 

 to absorb the dissolved, 

 starchy substance of the 

 endosperm. This cylinder 



Fig. 51 A. Cross-section embryo of corn epithelium is niccly shown 

 The cylinder epithelium above and large . , 4 . . , 



parenchyma cells below. (Pammel.) in the germinating wheat. 



During germination the scutellum remains within the pericarp. 

 "In many grasses there is in front of the embryo and oppo- 

 site the scutellum a small, scale-like appendage, the epiblast. 

 It is especially clear in Stipa, and yet better developed in 

 Zizania (where it is as long as the plumule), but it is entirely 

 lacking in many grasses (rye, maize and barley); generally it is 



Fig. 52. Maize trermlnating. Scutellum in front; r, primary root. In lower left 

 band corner, the plumule showing also second seminal roots from first node. (King) 



