356 



vigorous. Ill rirceiilaiul llic plaiil may attain a lieii:lit of at 

 least Ô3 cm. and in llic Norwefiiaii willow -lio^^s. as miicli as 

 176 cm. (NoHMANi. Oil the other hand, iiidividnals from exposed 

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

 the solitary flower scarcely reaches above the rosette-leaves 

 (f. pumilus Whbj,M. The dtînsity of the liair-coverinj,' varies also 



greatly and is no douhl partly 

 dependent upon the habitat of 

 the plant; plants which have 

 been growin^j 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 

 {Ï. flore pleno) in which all the 

 stamens are petaloid (Rosenv., I) ; 

 but the flower usually has five 

 p e r i go n e- 



13. R. acer. 



A, Base of nectary-leaf (Denmark; *'/i). Ih, 



Carpel from a hermaphrodite flower at time 



of flowering. B2, Carpel from a staminate yellowish-greeil 



flower; both from Denmark ('"/i); sec text. 



leaves and five 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 tlie 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 R. acer f. horealis Tractv. is as much as 

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

 by small beetles (Meligethus œneus] 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 



