390 The Physiology of Plants BOOK m 



been paid since. Its discovery in leaves of Yucca by 

 Meyer has already been mentioned. Parkin showed, in 

 1899, that it occurs in the bulbs and corms of certain 

 Monocotyledons. 



(d) Sugar. Of the various forms of sugar existing in the 

 green plant we had little knowledge prior to 1876. Most 

 of the monosaccharides were grouped together under the 

 name reducing sugar, as distinguishable thus from cane 

 sugar, which does not reduce Fehling's solution. It is 

 probable that these reducing sugars do not constitute 

 reserve materials. 



In the study of stored sugars the most interest centres 

 in saccharose, or cane sugar, which has long been known 

 as showing a very wide distribution. The view that it is 

 always a reserve material has been disputed, some authors 

 claiming that it is the first-formed sugar in photosynthesis, 

 as we have already seen. 



The evidence against its reserve character is based upon 

 certain observations on the ordinary nutritive processes. 

 It was shown to exist in the ungerminated barley grain by 

 Kiihnemann in 1875, but Brown and Morris ascertained 

 that the quantity increases threefold during germination, 

 instead of decreasing as reserve materials do. In 1882 

 Lepley showed that the starch of the maize is not formed 

 unless cane sugar is present in the juices of the plant. 

 Balland found the same state of things in 1888 in the 

 wheat, as did Girard in 1889 in the case of the potato. 

 Brown and Morris, in 1890, were able to cultivate young 

 excised barley embryos in a 2 per cent, solution of cane 

 sugar, in which indeed they thrived almost as well as if 

 they had remained in contact with their own endosperms. 



(e) Reserve Celluloses, Mucilage. These stores of carbo- 

 hydrate are treated of in connexion with the composition 

 of the cell wall. 



II. NITROGENOUS RESERVES, (a) Proteins. Little informa- 



