PLATE 14. 



A. — Stigma of Minnesota No. 21, a greenhouse tree, 24 hours after being selfed, 

 showing the condition of papillate cells in the stigma, pollen tubes, and also traces of 

 the stigmatic fluid. 



B. — Stigma of Minnesota No. 35, open to cross pollination, showing the condition of 

 a stigma three days after bloom, having withstood a rain of 0.87 inch which fell in the 

 two days previous, lasting in all 18 hours. Note the slight staining area of the stigmatic 

 fluid in which two pollen grains are embedded. 



C. — The turgid papillate cells in Sapa before receptiveness. 



D. — Opata. Same as C. Pollination has not yet taken place. 



E. — ^Abscission layer Minnesota No. 35, showing the cells of the layer 11 days after 

 bloom, 



F. — The surface at the abscission layer of Assiniboin after the style has fallen, 12 

 days after bloom. There appears to be no marked disintegration of the cells imme- 

 diately below the abscission layer, which suggests that in cutting off the style by this 

 method the breaking down of the middle lamella is restricted to a few cell layers. 

 108123°— 19 4 



