242 



1 . Ncphrophj/lhim. 



l'he, two species of lliis group wliicli liave been investigated 

 agree in the following points: — (1) The leaves are stalked 

 and palmately lobed, (2) the epidermis has undulating radial 

 walls, (3) glandular hairs are present, (4) the cells of the spongy 

 parenchyma are decidedly stellate (without a compact layer of tissue 

 under the epidermis), (5) the hydalhodes are exactly marginal, 

 without a cavity and without secretion of lime. 



The species differ most in regard to tlie thickness of the 

 outer walls of the epidermis, and the more or less decidedly 

 stellate form of the cells of the spongy parenchyma. The two 

 species can easily be distinguished from each other by these 

 features, while, however, their mutual relationship is very 

 distinctly expressed in their anatomy. A key to their deter- 

 mination by their leaf-anatomy would be as follows: — 



Outer walls of the epidermis: — 



(a) thin (2 — Z[x): S. cernua. 



(b) irregularly thickened (as much as 8 — 10,^^): S.rivularis. 

 Glandular hairs: — 



(a) long-stalked upon the upper, and sliort-stalked upon 

 the lower surface: S. cernua. 



(b) similar upon the upper and lower surface: S.rivularis. 



Saxifraga cernua L. (Figs. 1 and 2). 



This species according to Norman (1. c, pp. 303 — 04) is 

 a decidedly Arctic plant which extends beyond the tree-limit 

 697 metres and upwards. Grows both upon flat and sloping 

 ground, as commonly on the northern as on the southern side, 

 more rarely on the eastern and western sides. It prefers cold 

 and damp localities, among moss, along the banks of rivers, 

 upon stones in rivers, etc., and must be characterized as 

 decidedly hygrophilous. 



The leaves are long-stalked, reniformly-palmately lobed 



