Rosaceæ. 



33 



Potentilla Vahliana Lehm. 



Lit. Simmons, 1906. Wolf, 1908. 



This is an Arctic species which hves in North-West Green- 

 land, Arctic America and adjacent islands (Unalaschka) and 

 perhaps the Rocky Mountains. It occurs in dry localities 

 exposed to the sun, especially when they are gravelly, and 

 extends to the snow-line (Wolf, Lange). The alcohol ma- 

 terial was collected near Godhavn on Disco. 



Pot. Vahliana is a plant with a tufted growth; it has a 

 strong, long, multicipital primary root. An almost unbranch- 

 ed primary root on a small tuft from 

 Godhavn, which Warming had measured, 

 was 60 cm. long. The numerous shoots are 

 covered, almost for their whole length, with 

 dead leaves and remains of leaves, pressed 

 closely together, and upon the surface of the 

 tuft the living leaves hardly protrude above 

 the old dead ones (Fig. 12, A). Adventi- 

 tious roots, which may be fairly vigorous, 

 may arise from the shoots, but vegetative 

 propagation is undoubtedly only a rare 

 occurrence. The shoot-structure is monopo- 

 dial. The lateral flowering stems bear 1 — 2 

 small leaves and 1 — 2 large flowers. The 

 whole plant is covered with long, yellow 

 hairs. 



Anatomy. I have not examined the 

 roots. 



The structure of the rhizome agrees 

 in its chief points with that of Pot. palchella. 

 The pith is however considerably smaller; 

 the greater part of it was found to be com- 

 pressed; it contained starch, as did the other 



XXXVII. 



Fig. 12. Potentilla 

 Vahliana (God- 

 havn on Disco, 

 July 7). 



Ä. A shoot- complex 

 about 10 years old ; 

 about Vs. Above are seen 

 two flowering stems 

 and one which has 

 finished flowering pro- 

 truding from among 

 the living leaves; for 

 the rest, the greater 

 part of the shoots are 

 covered with dead 

 masses of leaves, 

 through which the re- 

 mains of the flowering 

 stems of previous years 

 are protruding. B, 

 Leaf; about V2. Drawn 

 by Eu g. Warming. 



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