Rosaceæ. 9 



the winter. Some shoot-apices are found raised as much as 

 10 cm, above the surface, while others are at the surface, and 

 others again are overgrown by the sphagnum of the bog. To 

 judge from specimens in the Copenhagen herbarium it is not 

 a fixed rule for the shoot-apices to die away during winter 

 in Greenland and Iceland, though they no doubt often do so; 

 normally the plant forms a monopodium till flowering begins. 

 In the event of the shoot-apex dying during winter there 

 will always be found a lateral bud upon the stem, situated 

 at the surface of the bog or below it, which can continue the 

 life of the plant. 



Irmisch does not understand why this plant is not 

 reckoned among woody plants as much, for instance, as Vac- 

 cinium oxycoccus, and Warming (1884) very properly calls it 

 a shrub. When Potentilla palustris is a chamæphyte it cer- 

 tainly resembles most closely a dwarf shrub, but the case 

 becomes more doubtful when the plant is a hemicryptophyte 

 or helophyte. Sylvén, Th. Wolf and Ascherson and Graeb- 

 NER^ mention it as an undershrub. 



Anatomy. The adventitious roots proceed from the 

 nodes of the stem especially during the second period of vege- 

 tation; they branch abundantly, but in each system there is 

 always a well-marked main axis. The anatomy has been 

 treated by Freidenfelt (1. c). I have, on the whole, found 

 the structure to be the same as that which he describes, but 

 in my material there were no roots with periderm. The epi- 

 dermis was characterized by being exceedingly small (Fig.4,A); 

 its contents were always brown in colour. In the periphery 

 of the cortex of the adventitious roots of the first order there 

 occur a few layers of cells with slightly thickened walls; inter- 

 cellular spaces are absent from this part; in the inner part 

 of the cortex the latter are large, and lysigenous lacunæ occur. 

 The endodermis is rather thick-walled. Freidenfelt records 

 that the primary cortex ultimately dies and falls off, a peri- 

 1 Synop. d. mitteleurop. Flora. Bd. VI, 1, p. 663. 



