Rosaceæ. 133 



individualization of the rosette-formed lateral shoots 

 of the runners. Food-storing roots often occur. It 

 lives through the winter without green leaves and 

 with its shoot-apex covered by scale-leaves. It is 

 typical for the leaf-structure to be slightly xeromor- 

 phic. 

 As features common to all the Rubiis-species may 

 be mentioned that they do not form rosette-shoots, that 

 the floral shoots are terminal ; and that they live through 

 the winter without green leaves ^ and with their \\inter- 

 buds covered by scale-leaves. Rubiis arcticus wanders 

 by means of its roots, and Rub. saxatilis by the develop- 

 ment of certain shoots into aerial runners the apex of 

 which is developed into a winter-bud situated at the 

 surface of the ground. Rub. chamæmorus has scale-leaf- 

 bearing underground runners. The leaf-structure in the 

 two first-named is mesomorphic and in the last-named 

 slightly xeromorphic. 



There are at least two points connected with the 

 shoot-structure of several of these Rosaceæ which 

 appear to be favourable to plants living in Arctic 

 climates, as regards the way the latter influence- the 

 plants, e. g. by desiccation (physiological desiccation) 

 and by the shortness of the growth-period. A great 

 many of the species, and more particularly those that 

 are true Arctic (see p. 121), are more or less highly 

 cæspitose, and may have in addition very closely packed 

 shoot-masses (closest in Pot. Vahliana); it appears 

 certain that by this method of growth the amount of 

 transpiration is lessened, in that the outer shoots of 

 the tuft protect the inner from the wind, and the 

 shoot-apices are surrounded and protected by the dead 

 masses of leaves. 

 1 See p. 93. 



XXXVII. 8 



