279 



closely investigated, are found (in spirit-material) precipitated 

 in some of the cells of the mesophyll which differ in no other 

 respect from the rest of the mesophyll. 



All the veins terminate in a hydathode (Fig. 23). The latter 

 opens into a cavity upon the surface of the leaf and secretes 



Fig. 24. Saxifraga Cotyledon. 



The epidermis of the leaf: A and B, Upper surface. С and D, Lower surface. 

 {A, B, C, D M2/i). 



lime abundantly which in many cases entirely fills the cavity 

 and spreads outside it (this is omitted in the figure). 



Bonnier has proved that dilferent specimens of this species, 

 collected partly in the Arctic and partly in the Alpine regions 

 of Central Europe, can be distinguished from each other by 



