Rosaceæ. Ш 



Summary. 



A. Account of the growlh-form of the species. 

 I. Microphanerophyte: Sorbus americana. 



Tree, low in growi^h. Lives through the winter 

 without green leaves; the shoot-apex is covered by 

 smooth bud-scales. The leaf-structure is mesomor- 

 phic. 

 II. Chamæphytes: Dryas octopetala and D. integrifolia. 



Dwarf shrubs with a primary root of long dura- 

 tion. The prostrate long shoots can be somewhat indi- 

 vidualized. In autumn the leaves die with the excep- 

 tion of a few half-unfolded ones at the shoot-apices. 

 The apex of the shoot is covered by the sheaths of 

 the young and dead foliage-leaves. The leaf-structure 

 is xeromorphic. 

 III. Hemicryptophytes: 



a. Dwarf shrubs or undershrubs. 



Potentilla palustris is a dwarf shrub (see p. 9) 

 which may be a hemicryptophyte, a chamæphyte^ 

 or a helophyte. The shoots with elongated internodes 

 Нл'^е through the winter without green leaves and with 

 their apices covered by the sheaths of the foliage- 

 leaves and by scale-leaves. Much wandering takes 

 place, as also vegetative propagation. The leaf-struc- 

 ture is slightly xeromorphic. 



Pot. tridentata is a creeping rosette-forming under- 

 shrub. Some of the summer-leaves may live through 

 the winter; there is no closed winter-bud. The leaf- 

 structure is xeromorphic. 



' See also Vahl, Growth-forms of some Plant Formations of Swed- 

 ish Lapland. Dansk bot. Arkiv, Bd. I, No. 2, Kobenhavn, 1913. 



