HYBRIDS OF JUGLANS. 



41 



seen. Although the development of this trichome was not studied par- 

 ticularly, the material examined indicated that the sequence of cell-divisions 

 may be the same as in the same type of trichome in both pure lines, and 

 thus it conforms with the sequence in cell-divisions in all of the other types 

 of multicellular trichomes in Juglans. Table 17 presents the measure- 

 ments made on the heads of this form of trichome. The average length 

 of the heads is 22.5 P-; diameter, 40.6 



FIG. 10. Trichomes of, ruffians calif ornica X J. ref/ia, F t : a, awn-shaped trichomes ( X 84); b to e, 

 disk-shaped trichomes (6 and d, X 800); c and e, X 535; / and </, long secreting trichomes (fir, X 

 535); h, transverse section of head of long secreting trichome of type with more than 4 cells in 

 head ( X 535); i to q, short secreting trichomes; i ( X 800) and.? (X 535), young trichomes; A-, tri- 

 chome from region of vein of leaf (X 535); I, trichome from dorsal leaf-surface (X 535); m, longi- 

 tudinal section of short secreting trichome (X 535); n top, trichomes from old leaf (X 535); q, 

 transverse section of head of short secreting trichome (x 830). 



The short secreting trichome is multicellular and consists of a 2 -celled 

 stalk and a head of 4 cells placed radially, as in both pure lines. Beyond 

 the first division of the young trichome, which is a transverse one, no stages 



