LEVULOSANES 131 



PARA-DEXTRANE AND PARA-ISODEXTRANE. 



These substances have been isolated from Boletus edulis 

 and Polyporus betulinus respectively. The former gives a 

 yellow colour with chlorzinc iodide, and the latter a blue when 

 treated with iodine and sulphuric acid. Both give glucose on 

 hydrolysis. 



LEVULOSANES. 

 INULIN. 



This substance is commonly found as a reserve food-stuff, 

 of the same nature as starch, existing in a state of solution in 

 the cellsap of a number of plants belonging to the natural 

 order Compositae, e.g. in the tubers of the dahlia and artichoke 

 (Helianthus tuberosus\ and in the fleshy roots of the chicory 

 (Cichorium Intibus}. It has also been described as occurring in 

 the following natural orders : Violaceae, Malpighiaceae, Drose- 

 raceae, Candolleaceae, Goodeniaceae, Campanulaceae, Lobelia- 

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

 Algae, e.g. Neomeris. 



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. 113). 



Thus in Iris pseudacorus 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. Inulin is not formed as such in the leaves 

 but in the places of storage by the condensation of the sugars 

 synthesized by the leaf.* 



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 f 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 Schizo* 



* Colin : " Compt. rend.," 1918, 166, 224, 305. 



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



9* 



