WALNUT. 



25 



and about 40 [j, in diameter. The guard cells are narrow, resulting 

 in a comparatively wide opening. One guard cell is sometimes 

 smaller than the other or apparently abortive. 



In the transverse section (fig. 8, B) the outer periderm tissue is 

 found to consist of three or four layers of cells and to reach a thick- 

 ness of about 40 \L. The thin layer of inner periderm tissue resembles 

 that of the walnuts already described. The endosperm consists of a 

 single layer of cells about 15 to 20 ^ thick, while the epidermis of the 



A B 



FIG. 8. Pecan: A Epidermis of integument showing elongated cells (X175); B Sec- 

 tion of integument and superficial tissues of kernel (X175). 



cotyledons is about 10 p thick. The parenchyma of the embryo 

 resembles that of the Persian walnut. The aleurone grains reach a 

 maximum diameter of about 10 \L with an average of 4 to 5 \L. 



LITTLE SHAGBARK OR SHAGBARK HICKORY. 



(Ilicoria ovata (Mill.) Britt.) 



The common hickory is of wide distribution and the nuts are too 

 well known to require description in this place. Unfortunately the 

 shell is rather thick and the nut appears to be less variable than the 

 pecan. As wild nuts are usually abundant little has been done along 

 the line of searching for improved varieties worthy of cultivation. 

 Woods and Merrill * report 37.8 per cent kernel, while Lazenby 2 

 gives 32 per cent. Nuts obtained by the writer from three different 

 trees growing in the same locality in eastern New York gave 32.8, 

 35.4, and 37.1 per cent of kernels, respectively. 



Histology. The epidermal cells of the periderm average about 30 

 to 40 [A in diameter. They are more angular than those in most of 



1 Maine Agr. Exper. Sta. Bui. 54, p. 75. 



2 Loc. cit., p. 101. 



