i54 
R. S. Adamson. 
are fully differentiated. In structure the root-cap is also remarkable 
(Fig. 6); it is of considerable thickness, from twenty to twenty- 
five layers of cells being present in some cases above the apex. 
Fig. 6. Longi tudinal median section of young root cap. 
Fig. 7. Transverse section through root cap, along line A-B, in Fig. 6. 
The tissue forming the cap appears to be differentiated into two 
parts, a central portion over the growing-point of the root 
(Fig. 7) and a peripheral portion (see Figs. 6 & 7). These regions are 
