Rosaceæ. 65 



varies greatly; I have found them to be from one to about 

 10 cm. long; the longest are often found at the periphery <>f 

 the tu lis. 



Haglund (1. c.) records that the leaves of D. octopetala die 

 away during winter; others find that the leaves remain green 

 during winter, viz. SCHRÖTER, Hartz (1895a, p. 182) and 

 Jonsson (cf. Fig. 26); in my material there were specimens 

 collected by Jonsson in January, and they agreed exactly 

 with his figure and in this manner D. octopetala also behaves 

 in the Botanic Garden in Copenhagen. Finally, Warming 

 remarks in his notes that D. integrijolia has leaves which 

 live through the winter. The oldest leaves on the sin ml 

 wither in the autumn hut as iigure 26 shows there area lew 

 half expanded young leaves at the apex of the shoot and 

 these live through the winter. Scale-leaves are not developed 

 (cf. Haglund); the shoot-apices are protected by the leaf- 

 sheaths. 



Anatomy. The root -system as mentioned above is 

 characterized by a vigorous main root which bears vigorous 

 branches. The absorbent roots are richly branched and then 

 apices are encompassed with a thick mantle of fungal hyphæ. 

 Hesselman figures mycorrhiza of D. octopetala which resemble 

 I hose of the Cupulijerae; D. integrijolia also has mycorrhiza. 

 Hesselman also illustrates the structure of the root by 

 several figures. 



The central cylinder in the primary root is surrounded 

 by a vigorous endodermis and in the innermost layer of the 

 cortex the radial walls are highly thickened in the middle, 

 so that the transverse section of the wall shows an almost 

 circular figure. Periderm is developed in the outermost 

 layer of the pericycle, and gradually as the periderm and 

 the secondary wood grow the cortex dies and is thrown off 

 together with the hyphæ. In older roots it attains a consider- 

 able thickness: it consists exclusively of cork-cells which 

 w.wii. 5 



