LEVULOSANES 



115 



the following natural orders : Violaceae, Malpighiaceae, Drose- 

 raceae, Candolleaceae, Goodeniaceae, Campanulaceae, Lobelia- 

 ceae, Myoporineae, Liliaceae, and Amaryllidaceae ; also in some 

 Algae, e.g. N corner is. 



Inulin, or closely allied substances, are not infrequently 

 found in company with starch, especially in some Monocoty- 

 ledons ; and the same peculiarity in its occurrence, as has al- 

 ready been remarked upon in connexion with the occurrence 

 of starch in monocotyledonous plants, obtains (p. 97). 



Thus in Iris pseiidacorus starch is present but not abundant, 

 in Iris Xiphium both starch and inulin are present in quan- 

 tity ; Scilla nutans has inulin but no starch, while Scilla 

 sibirica, and also Hyacinthus and Muscari botryoides have both 

 starch and inulin. 



It is of interest to find that the nature of the reserve carbo- 

 hydrates may often be correlated to the habitat of the plant. 

 Parkin * points out that these reserve substances of aquatic 

 plants and of plants inhabiting wet situations take the form 

 of starch, e.g. Sparganium, Alisma, Listera, Orchis, and Schiso- 

 stylis ; 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 



* Parkin : " Phil. Trans. Roy. Soc, Lond.," B., 1899, 191, 169. 

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



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