TRITICUM 



177 



colorless except for a chlorophyllose region one cell in thickness, 

 adjacent to the inner epidermis; but there may also be chloroplasts 

 in the subepidermal cells along the furrowed portion of the young 

 pericarp. As maturity approaches, the cells of the inner epidermis 

 fail to keep pace with the growth of the adjacent cells and become 

 separated, forming the characteristic tube cells of the ripe pericarp. 



D 



Fig. 80. A-D, transections showing the developmental changes occurring in the pericarp, 

 integuments, and nucellus during the maturation of the grain : a, the cross cells of the peri- 

 carp; b, inner epidermis of pericarp; c, outer integument of ovule; d, inner integument of 

 ovule ; e, outer layer of nucellus ; /, cells of nucellus ; g, aleurone layer. (Redrawn from Per- 

 cival. The Wheat Plant, Duckworth and Co.) 



Shrinkage and desiccation cause a compression of the cells which 

 come into intimate contact with those of the testa and in this man- 

 ner the combined fruit-seed coat of the caryopsis is formed. 



I. 



1. 



3- 



LITERATURE CITED 



Avery, G. S., Jr., "Comparative anatomy and morphology of embryos and 



seedlings of maize, oats, and wheat." Bot. Gax_. 8p: 1-39, 1930- 

 Bessey, C. E., "The structure of the wheat grain." Neb. Agr. Exp. Sta. Bull. 



}2: 100-114, 1894. 

 Boyd, Lucy, and Avery, G. S., Jr., "Grass seedling anatomy: The first 



internode of Avena and Triticum." Bot. Gaz- 97- 765-779, 1936. 

 Brenchley, W. E., "On the strength and development of the grain of wheat 



(Triticum vulgare)." Ann. Bot. z^: 117-139,1909. 



