Rosaceæ. 117 



tation to life in bogs in these species. It is true that 

 respiration in the inner part of the shoots is facilitated 

 by the presence of the intercellular spaces in the peri- 

 derm, but the comparison with aërenchyma does mol 

 appear appropriate when we consider that species from 

 extremely dry habitats, such as Pot. iridentata, Pot. nivea, 

 Alch. alpiria and others have a quite similar structure 

 of the periderm. A contribution to the explanation of 

 the structure of the periderm in these Rosaceae may 

 perhaps be found in the fact that it no longer functions 

 only as a protection from excessive transpiration, as for 

 instance in Dryas, but that it has also developed into a 

 very important starch-storing organ; at any rate, a peri- 

 derm with this function requires an ample supply of 

 oxygen so that the necessary condensations and hydro- 

 lyses can take place in it. — It may be mentioned that 

 a similar periderm also occurs in the roots of the species 

 which have been investigated, with the exception of Dryas 

 and Rubus arcticiis. As regards this point the reader is 

 referred to Martha Bunding 1 who has investigated the 

 root-cork in many Rosaceae and finds as a rule intercellular 

 spaces in the herbaceous species, but not in the woody 

 or shrubby (cited from Freidenfelt). 

 E. Special food-storing organs are absent except in Pot. an- 

 serina which frequently has spindle or club-shaped food- 

 storing roots of a peculiar anatomical structure. Other- 

 wise reserve food-material is found in the root (many of 

 the species have primary roots of long duration and con- 

 siderable size) and in the perennial portions of the shoots. 

 The tissues which contain reserve food-material are the 



Structure of the Cork Tissues in Roots of some Rosaceous genera. 

 Publ. of the Univer. of Pennsylv. New Ser. No. 5. Contrib. fr. 

 the Bot. Laborat., Vol. 2, 1898. (Unfortunately, the paper has 

 not been available to me). 



