WALNUT. 21 



transverse section (fig. 6, B) the outer periderm tissue is found to 

 onsist of a single cell layer 30 to 40 y. in thickness. The inner layer 

 is a thin, dark-colored tissue not unlike that of the Persian walnut. 



The endosperm consists of two or three layers of cells, forming a 

 tissue of quite uniform thickness, amounting to 30 to 40 JJL. It ad- 

 heres closely to the integument. The thick outer walls of the aleurone 

 cells form a hyaline layer suggesting the remains of the perisperm. 

 The epidermis of the cotyledons consists of small cells 12 to 16 \L in 

 thickness. The parenchyma of the cotyledons is much like that of 

 the Persian walnut, though, less tendency to a linear arrangement of 

 the cells was observed. The aleurone grains vary up to 16 \L in 



A 



FIG. 6. Japanese walnut : A Epidermis of integument showing coiled guard cells 

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



diameter, but probably do not average more than 10 JJL, differing from 

 those of the Persian walnut mainly in size. 



CALIFORNIA BLACK WALNUT. 



(Juglans calif ornica Watson and Juylans calif arnica hindsii Jepsou.) 



Since the native California walnut was shown by Watson to be 

 distinct from /. rupestris, it has been the custom to apply the name 

 /. calif ornica to all of those nuts known as California black walnuts. 

 Eecently two distinct types of California walnuts have been recog- 

 nized, and Jepson has given the name /. hindsii to the larger form, 

 which is found in central and northern California, restricting the 

 name /. califomica to the more shrubby type with smaller nuts, 

 which grows in the southern part of the State. /. hindsii is not, 

 however, universally accepted as a distinct species. Its resemblance 

 to the eastern black walnut, J. nigra, would lead to the suspicion that 

 it is a hybrid between that species and /. calif ornica, a supposition 



