356 



vigorous. In Greenland the plant may attain a height of at 

 least 53 cm. and in the Norwegian willow-bogs, as much as 

 176 cm. (Norman). On the other hand, individuals from exposed 

 localities, are found which measure only 4 cm., and of which 

 the solitary flower scarcely reaches above the rosette-leaves 

 (f. immilus Whbg.l. The density of the hair-covering varies also 



greatly and is no doubt partly 

 dependent upon the habitat of 

 the plant; plants which have 

 been growing in copses are often 

 almost entirely glabrous, while 

 those from exposed localities 

 may be covered with a dense 

 covering of white or yellowish- 

 brown hairs (var. Lindholmiana 

 Berl.). 



In Greenland a form has 

 been found with double flowers 

 \L flore pleno] in which all the 

 Fig. 13. R. acer. stamens are petaloid (Rosenv., I) ; 



^, Base of nectary-leaf (Denmark; ед. Bi, b^jt the flowerUSUally haS fivC 

 Carpel from a hermaphrodite flower at time 



of flowering. iÎL>, Carpel from a staminate yellowish-greeu p 6 Г 1 g П 6- 



flower; both from Denmark ('Vi); see text. 



leaves and hve nectary- 

 leaves, glistening as if with oil; these latter have pocket-shaped 

 nectaries the free edge of which varies greatly in form (Fig. 13, A). 

 The numerous, extrorse anthers overtop the head of carpels, 

 which is low in growth before pollination. The diameter of 

 the flower is between 1-5 and 2"ôcm.; in Nova Zembla the 

 diameter of that of B. acer f. borealis Tractv. is as much as 

 3'0 cm. (Ekstam). In Denmark the flower is eagerly visited 

 by small beetles [Meligethus ceneus) and flies; Lindman found, 

 besides several species of flies, a few Macrolepidoptera; Ekstam 

 noticed flies. 



In the flower-bud. the stamens overtop the carpels; but 



