SEEDS AND SEEDLINGS 



121 



root lies near the tip of the grain and is enclosed in a delicate 

 sheath ; at the opposite end is the plumule; the hypocotyl or stem 

 is very short and connects the radicle and plumule ; attached to 

 the hypocotyl and lying just back of the embryo is the large 

 cotyledon or scutellum. The remainder of the grain is made up 

 of the endosperm,, which in this case is mainly starch but sur- 

 rounded by the gluten layer. The seed coats and ovarian walls 

 unite to form a thin horny layer (Fig. 86 ). This is the grass type 



em 



FIG. 86. (a) Diagrammatic under-side view of a grain of corn showing the embryo (em) 

 and the layers of food; (6) longitudinal section of corn showing same parts; (c) cross-section of 

 grain of corn showing the same parts. 



of seed and is characteristic of the grasses and many other 

 monocotyledonous plants. 



Germination of the Corn. In germination the root sheath 

 is pushed out for a short distance ; this is followed by the emerg- 

 ence of the root tip through the end of the sheath. Two adventi- 

 tious lateral roots are then formed, one in the axis of the 

 plumule and scutellum and the other on the opposite side of the 

 hypocotyl. Secondary roots are produced from the primary 

 root. The conical roll of leaves emerges from the upper end of 



