HYBRIDS OF JUGLANS. 



49 



The reasons for this curious behavior are not apparent, but an explanation 

 may possibly be found in the following facts: The trichome in question was 

 seen only on the veins and is the last of the types to appear, that is, the 

 older leaves only showed its presence, although exactly when in the de- 

 velopment of the leaf this type was formed was not learned. Again, the 



Fig. 15. Trichornes of Juglans californica < Juglans nigra, F 2 , plant 4. (Unless otherwise 

 stated the trichornes are of the type which has a head of more than 4 cells.) a, third cell- 

 division of trichome; 6, long secreting trichome undergoing the sixth cell-division; c, 

 second division of the stalk, which thus occurs in different sequence than in the regular 

 type; d, same stage as before; e, 2 trichornes, showing stalk of 4 cells and the third division 

 of the head ; /, trichome with a head of 8 cells, of which 3 were seen in the adjoining sec- 

 tion, and the fifth stalk-cell in the process of being cut off: g, abnormal trichome of long 

 secreting type. (All figures X 1200.) 



great irregularity may be owing to the hybrid nature of the plant, as no 

 such inconsistencies were observed in the pure strain nigra. Or, the fact 

 that the number of cells composing the trichome is relatively large may be 

 a factor which should be considered in this connection. This irregularity 

 is all the more striking because of the perfect consistence in the sequence 

 of cell-divisions which was observed in the smaller type of long secreting 

 trichome and in the short secreting trichome as well. 



