48 



HEREDITY AS ILLUSTRATED BY TRICHOMES. 



divisions of the head and of the stalk appear to take place independently, 

 which is especially and perhaps solely true of rather old trichomes. For 

 example, a trichome was seen which had a head with 7 nuclei, but a stalk 

 with the fifth cell just being: cut off, and another trichome was seen which 

 was forming' the fifth or sixth cell in the head, although the stalk con- 

 sisted of 9 cells. 



FIG. 14. Disk-shaped trichomes of Juglans cali/ornica X Juglans nigra, F 2 , plant 1: a, trichome 

 with head consisting of 4 cells, of which 2 are in the process of dividing, and a 1-celled stalk; 6, 

 trichomes with head of 6 or 7 cells, and a, stalk of 1 cell which is undergoing division; c, tri- 

 chome with 1-celled stalk and 4-celled head; d, trichome with 2-celled stalk; e, transverse sec- 

 tion of head to show the formation of octants; /, trichome with a head of 7 or 8 cells and a 

 1-celled stalk. (All figures X 1200.) 



Additional evidence as to irregularity in the number of cells making: up 

 the larger type of long secreting trichome was observed in the unusually 

 large number of head-cells. A trichome was seen, and is shown in fig. 16, 

 which had a head of 14 cells, although there were only 6 cells in the stalk. 



