288 



In all the specimens examined by me I found the distri- 

 bution of the stomata to differ somewhat from that mentioned 

 by Lazniewski. His Fig. 1 1 (1. c, p. 239) shows the stomata to 

 be below the line A — B. But in all the Arctic specimens the 

 stomata-bearing band begins still higher up and only the 

 oblique surface upon which the hydathode is situated is devoid 

 of them. In the fully expanded specimens that part of the 

 leaf which bears the stomala, is not at all shielded from 

 exposure to light, in fact, the stomata occur especially 

 upon the strongly exposed parts of the leaf which possess 

 palisade-cells, with the exception only of the oblique surface 

 bearing the hydathode. Hence we must resort to quite a diffe- 

 rent explanation of the distribution of the stomata: — They 

 are absent from the oblique surface bearing the hydathode, 

 which is the only part of the leaf that in the bud-condition 

 of the shoot is exposed to light and air; we have here an 

 instance of a primitive bud-protecliou which comprises only 

 the very young leaves, while already the oldest leaves of the 

 bud, which are exposed to the elements, are somewhat expanded 

 before winter sets in. 



Besides, the stomata are absent from the base of the leaf, 

 — where I think they might be expected to occur in large 

 numbers if Lazniewski's hypothesis should also apply to the 

 Arctic species. The absence of stomata from the base of the 

 leaf is to be connected with the fact that the "leaf-base" is in 

 reality the morphological leaf-stalk (below the common start- 

 ing point of the veins), where neither palisade-cells nor sto- 

 mata occur (compare S. groenlandica and S. }iypnoides)\ conse- 

 quently the other Saxifraga-species have no stomata upon 

 their leaf- stalks. Lazniewski's assertion that the stomata are 

 hidden in "interfoliar spaces free from air-currents" 

 does not apply at all to the Arctic specimens, as (1) the sto- 

 mata are situated chiefly in the parts of the leaf possessing 



