22 



HEREDITY AS ILLUSTRATED BY TRICHOMES. 



Besides this type of long secreting trichoma there may be another kind 

 with a larger number of cells in the head and also more than 4 cells in the 

 stalk. This form of trichome, doubtful in Juglans calif ornica, was often 

 met in Juglans nigra, under which it will be described, and in the hybrid 

 Juglans calif arnica X Juglans nigra. A few trichomes with 6 stalk-cells 

 were found in Juglans calif ornica, one of which is shown in fig. 5, h, but 

 none were seen under conditions that made it possible to surely determine 

 the number of cells in the head. 



FiQ. 5— Trichomes of Juglans californica: a to h, various stages in the development of long 

 secreting trichomes (a, c, d, /, and ly X 535; 6 x 1200); i to o, mature and young short 

 secreting trichomes (X 536). 



In studying this type of trichome it was found best to measure the head 

 only, since the entire trichome, which is relatively long, varies consider- 

 ably. Wherever possible the position of the trichome on the leaf is given, 

 but whenever this is not done it is to be understood that in every instance 



