88 



R. A. BRINK 



the incoming nutrients is diverted to the integuments. As a result this 

 tissue frequently becomes hyperplastic. The overgrowth in the case of al- 

 falfa characterizes the inner integument. As Dr. Cooper observed, it begins 

 at a point opposite the distal end of the vascular bundle where the concen- 

 tration of nutrients maybe assumed to be the greatest. The inner integument, 

 which is normally two cell layers in thickness, becomes multilayered and 

 somewhat callus-like in the region of the greatest mitotic activity. This pro- 

 nounced overgrowth of the inner integument quickly reacts upon the endo- 

 sperm, further impairing its development. In the seeds which fail, a complete 



48 72 % 120 



Time in hours after pollinatior\ 



m 



Fig. 5.1— Increase in number of cells in embryo and in number of nuclei in endosperm 

 following self- {broken line) and cross-fertilization {continuous line). After Brink and 



Cooper, 1940. 



