376 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



PERFORATION. 



This has come to be one of the most serious troubles of the walnut 

 grower during recent years. The effect is that shown in Fig. 93 and 

 consists in a non-development of the outer hard layer of the shell. 

 The meat or seed of the walnut is covered normally by four different 

 layers of tissue. The first of these is the pellicle or seed coat, the thin 

 membrane just over the meat which adheres closely to it and follows 



I 



'"' <* 

 ( 



f*. 



FIG. 93. "Perf oration" of walnuts. 



all the convolutions and irregularities of its shape. Outside of this 

 is what we call the shell, which consists of two distinct layers, a thin, 

 inner, parchment-like one, forming the lining of the shell, and a hard, 

 bony outer layer. The fourth coating mentioned is composed of the 

 husk on the outside of the nut which opens and allows the nut to fall 

 out at maturity. In perforated nuts the hard shell is not actually per- 

 forated, but rather fails to develop. In such nuts the meat and pellicle 

 develop normally and over them the thin, inner lining of the shell. 



