Evidence from Somatic Histogenesis 



55 



as it almost certainly will be, that the cytoplasm is "hered- 

 itary substance" for the production of spicules, the reverse 

 of Conklin's generalization that the cytoplasm determines 

 the larger taxonomic features of animals while chromatin is 

 the seat of the inheritance factors for "filling in details" 

 turns out to be true. Species-marking details are just 

 what we are able to see the cytoplasm fill in. 



The "Hairs" of Higher Plants 



For a few more instances of species characters in multi- 

 cellular organisms brought down to single cells, we turn to 

 the plant world. 



FIGURE 52. FIGURE 53. FIGURE 54. 



FIGURE 52. TRICHOMES OF PAPAVER ORIENTALS (AFTER CANNON). 



FIGURE 53. TRICHOMES OF P. PILOSUM (AFTER CANNON). 



FIGURE 54. THICHOMES OF P. SOMNIFEHUM (AFTER CANNON). 



The "hairs" or trichomes borne on the leaves, flowers 

 and smaller stems of innumerable flowering plants are 

 usually composed of only a few cells, so that the characters 

 they have are often referable to the individual cells. Can- 

 non has lately investigated these structures in several groups 

 of plants, and while he was not aiming at the particular 

 question now occupying us, some of his results are quite to 

 the point for this discussion. An example of particularly 

 distinct specificity of the hairs is presented in the following: 

 "The trichomes of the three species [of poppy] are similar 



