TRITICUM 



155 



"the coleoptile as a third leaf." Avery (i) regards the scutellum 

 as the cotyledon or first leaf of the plant, the coleoptile as the 

 homologue of a foliage leaf or the second leaf, and the leaf distal 

 to it as the third leaf. He states that "the epiblast, when present, 

 cannot be considered a rudimentary cotyledon." More recently 

 Boyd and Avery (3) reaffirmed this view, stating that "the cole- 

 optile is the first leaf above the single cotyledon." 



All of these investigators agree that the use of the term mesocotyl. 



— mer reg 



mer reg 



Fig. 66. A, median side longisection of dormant embryo ; B, the same, 7 days old in which 

 slight elongation of the axis above the scutellar node is taking place ; C, the same, in a month- 

 old plant showing the elongated second internode sheathed by the coleoptile. Meristematic 

 regions of elongation are shown with dashes : colp, coleoptile ; colp no, coleoptilar node ; 

 coir, coleorhiza ; mer reg, meristematic region ; pri rt, primary root ; scu, scutellum ; scu no, 

 scutellar node. (After Avery.) 



as originally applied to the first internode, is misleading, since 

 it implies that the first internode is a part of the cotyledon. While 

 differences in terminology do not modify the actual structure, 

 they do tend to create confusion in the literature; and it is desirable 

 that a uniform nomenclature be applied to the embryo and seedling 

 of the grasses. 



Germination. — In germination, the wrinkled surface of the 

 pericarp over the embryo becomes smooth, and the entire wall is 

 stretched. Following the rupture of the pericarp, the coleorhiza 

 emerges, and the enlargement of the epiblast and other embryonic 



