WALNUT. 19 



nuts from 18 to 20 per cent. The writer, however, obtained 21.3, 

 24.4, and 24.6 per cent from three average commercial samples. 



Histology. The epidermal cells of the seed coat, though resem- 

 bling those of the Persian walnut, are more angular and have a 

 clouded, opalescent, or smoky appearance, due apparently to the color 

 of the cell contents (sec fig. 4, A). The stomata are roundish or 

 slightly broader than long, measuring about 45 to 50 [/, by 50 to GO [A. 

 The guard cells are usually narrower than those of the Persian walnut 

 and the butternut, and are about as numerous as those in the latter 

 species. They are often more coiled than those in the other species 

 thus far considered, suggesting somewhat the character so conspicu- 

 ous in the two following species. 



In the transverse section (fig. 4, B), the outer periderm tissue is 

 seen to consist of a single layer of cells of very even thickness, 



A B 



FIG. 4. Black walnut : A Epidermis of integument showing opalescent character of 

 cell contents (X175); B Section of integument and superficial tissues of kernel 

 (X175). 



amounting to about 20 \L . The cells contain much tannin, the pres- 

 ence of which is readily demonstrated by treatment with ferric 

 chlorid. The inner layer of periderm cells is like that of the 

 butternut. 



The endosperm consists of a single layer of cells, occasionally di- 

 vided tangentially, and often containing irregular yellow masses. 

 The cotyledon tissues are like those of the other walnuts described. 

 The aleurone grains closely resemble those of the butternut. 



JAPANESE WALNUT. 



(Jiifflans sicboldiana Maxim., J. cordiformis Maxim., and J. mandshurica 



Maxim.) 



Three types of walnuts, natives of Eastern Asia and Japan, were 

 described by Maximowicz, who gave them- the names mentioned above. 

 The first is a fair-sized ovoidal nut, the second is smaller and decid- 



