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 /*: diameter, 40.6 



FIG. 10. Trichomes of. fuglans californicn J. rei/ia, F,: <i, awn-shaped trichomes ( W); b tot-, 

 disk-shaped trichomes (6 and d, X SOOj; c and c, .">3o ; / and </, long secreting trichomes iff, X 

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

 head ( X 585); i to (/, short secreting trichomes; / ( ' 800) and.) ( < F3!>), young trichomes; k, tri- 

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

 tudinal section of short secreting trichome ( < 535): n to p, trichomes from old leaf ( ~&~>); 17, 

 transverse section of head of short secreting trichome ( < 8M). 



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 



