HYBRIDS OF JUGLANS. 



47 



transverse in the stalk, the fourth and fifth are longitudinal 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- 



f 



FIG. 13. Trichomes of Juglans californlca X Juglans nigra, F 2 , plant 1: a to c, long 

 secreting trichomes, showing sequence of cell-division of stalk; d 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- 



