132 THE CARBOHYDRATES 



sty Us ; whereas, on the other hand, inulin, generally associated 

 with sugar, is the characteristic carbohydrate reserve in those 

 Monocotyledons inhabiting dry situations, e.g. Allium, Aspho- 

 delus, Anthericum, Yucca, Tritona, Iris Xiphium, etc. 



In this connexion * reference must be made to the work of 

 Lidforss, who showed that plants inhabiting wet situations 

 fall into two distinct categories ; those like Elodea, Chara and 

 Stratiotes, which hibernate at the bottom of the pond or stream, 

 contain starch but no sugar ; while those which live on the 

 banks where their rhizomes, or other organs of storage, pass 

 the winter out of the water, e.g. Myosotis* and Menyanthes> 

 contain sugar during the winter months. In the former case 

 a temperature of - 2 C. to - 4 C. is fatal, while in the latter 

 case the death point is about 7 C. 



This peculiarity also obtains for many arctic plants ; 

 Miyake, Wulff, and others have shown that cold, which means 

 physiological dryness, is conducive to sugar production, so that 

 arctic plants frequently exhibit but a small amount of starch, 

 and relatively large quantities of sugar. Stahl has shown that 

 the leaves of mycotrophic plants, which generally show a feeble 

 transpiration, seldom contain starch, its place being taken by 

 glucose. Lidforss also has shown that the winter green vege- 

 tation of Sweden is characterized by the absence of starch from 

 the leaves, the mesophyll, in its place', containing relatively 

 large quantities of sugar, and sometimes oil during the winter 

 months. In summer the leaves of these plants contain 

 starch, which, on the advent of winter, is converted into sugar, 

 from which starch is formed on the rise of temperature in the 

 spring, f 



Then, again, it is not uncommon to find sugar stored in the 

 periderm of trees and in the leaves of evergreen plants during 

 the winter ; starch, however, may be found in the leaves of 

 evergreen trees during the cold season, its presence being due 

 to feeble photosynthesis. 



Reference may be made here to the well-known fact that 

 potatoes turn sweet on exposure to cold. This conversion 

 of starch into sugar is most active at o C., and the action de- 

 creases with the rise in temperature, so that above 7 C. no 



* See Blackman : " New Phyt.," 1909, 8, 354. 



t See also Maximow: " Ber. deut. hot. Gesells.," 1912, 30, 52. 



