ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 469 



carbonic acid and the elimination of oxygen) only takes place under 

 the influence of light, its action goes on also under the influence of 

 the dark or ultra-violet rays. They remark that the definition of 

 luminous radiations is subjective, and varies with individuals ; that 

 one of the principal absorption-bands of chlorophyll is cut by the 

 limits of the visible spectrum at the violet end, and that the rays 

 which correspond to the second part of the band are invisible to our 

 eyes. As a proof of their position they give the following table : — 



Eelation of the volume of carbonic acid 

 given off to that of oxygen absorbed. 



Elements of Lactose in Plants.* — M. A. Miintz, after describing 

 the methods by means of which mucilage, gums, pectous and mucous 

 bodies can be obtained from plants, gives the percentage of these 

 substances found in various plants used as food by man and domestic 

 animals. 



Amongst grains, for instance, wheat contains 0*5 per cent, of 

 pectose, which is situated chiefly in the bran ; and 0*5 to 1 • of 

 gum, chiefly in the flour ; barley contains • 9 of pectose, 2 • 8 of gum. 

 Amongst the LeguminosJB, white beans, broad beans, &c., have 2*0 to 

 4 • per cent, of pectous material, chiefly as pectate of lime, in the 

 testa. In the oleaginous forms, such as clover and lucerne, a large 

 quantity of gum, as much as 45-0 per cent., is found. Amongst 

 fruits, apples contain 0-8 pectose, 0*5 gum; plums, 0-6 pectose, 

 1*2 gum. Roots and tubers are generally rich in pectose and gums, 

 e. g. carrot contains 1 • to 2*0 per cent, of pectose, and • 5 gum ; 

 potato, • 6 and • 8. Greens contain pectate of lime ; cabbage, • 6 

 to 1 ' 2 per cent. ; endive, from 0*5 to 1-0 per cent, of pectic acid. 

 Amongst forage plants usually eaten by farm animals, grasses contain 

 1*1 to 4*5 of pectose and 1*0 to 3 • of gum, and so on. In fer- 

 mented liquors, gums are always present, e. g. beer contains 10 grams 

 per litre ; cider, 5 grams. In all these cases the pectic acid obtained 

 from the plant is identical, but the gums are either Itevorotatory as 

 in fruits, or dextrorotatory, as in the Leguminosae. By considering the 

 above results it is possible to calculate what proportion of the prin- 

 ciples able to form galactose, may be consumed by a milch-cow yield- 

 ing a known quantity of milk per day. And the author finds (1) that 

 the gums, mucilage, and pectous bodies of plants contain, in the 

 products of their decomposition, galactose identical with that of milk 

 sugar. (2) That these mucous substances exist in vegetable foods in 

 such quantity that they can furnish galactose, which enters into the 



♦ Comptes Rendus, cii. (1886) pp. 681-4. 



