HYBRIDS OF JUGLANS. 



47 



transverse in the stalk, the fourth and fifth are longritudinal in the head. 

 To this point the sequence of divisions of the short secreting and long 

 secreting trichomes is the same. The sixth division occurs in the upper 

 stalk-cell and is transverse, and the seventh and last cell-division is a cross- 

 wall in the lower stalk-cell. The successive divisions are illustrated by the 

 accompanying figures, which also indicate the sequence of cell-divisions 

 in the short secreting trichome. 



The results of the study on the second type of long secreting trichome, 

 while not entirely satisfactory, indicate that it is a fundamentally different 

 form than the type with a smaller number of cells. The youngest stages 

 of this trichome either were not seen or could not be identified as belong- 



FiG. 13.— Trichomes of Juglans californica X Juglans nigra, Fj, plant 1: a to c, long 

 secreting trichomes, showing sequence of cell-division of stalk; cJ to /, some 

 stages in development of short secreting trichomes. (a to c, X 1200 ; c, X 840 ; d to 

 /, X 1200. Reduced one-fourth.) 



ing surely to the trichome. A trichome with 5 cells, of which 2 were of 

 the head, had undergone division of the lower of the 2 stalk-cells. An- 

 other trichome having a head of 4 cells had just experienced the division 

 of the lower stalk-cell. That there is some irregularity in the sequence of 

 division is shown by another trichome in which the stalk consists of 4 cells, 

 although the third cell-division of the head is just taking place. The cell- 



