THE RESERVE MATERIALS OF PLANTS. 477 



the shoots of the sugar cane and in the fleshy root of the 

 beet, which are the two sources of the surar of commerce. 

 But there is a considerable body of evidence pointing to its 

 being the most immediately available form of nutritive 

 sugar, though it is apparently not the form most prominent 

 in the circulating carbohydrates. Brown and Morris (35) 

 in a paper already quoted indicate a probability that it is 

 the first formed sugar in the processes of constructive meta- 

 bolism, and constitutes the first reserve product on which 

 the cells of the leaf feed. In such cases, what is formed 

 beyond the immediate need of the cells is transformed into 

 the more stable form of starch, as already described. Its 

 nutritive value seems to be higher than that of any other 

 sugar found in the vegetable tissues. Brown and Morris 

 cultivated young excised barley embryoes in a 2 per cent, 

 solution, and found that the growth they showed was almost 

 equal to that they displayed when grown on the natural 

 endosperm of the barley grain. In a 4 per cent, solution 

 even greater growth was noticeable, but a greater concen- 

 tration did not give good results. Cane sugar exists as 

 such in the ungerminated barley grain as proved by Kiihne- 

 mann (36) in 1875, and Brown and Morris showed that 

 during germination the quantity was increased threefold. 

 It appears further from their researches that the increased 

 amount is derived from maltose by the activity of the 

 growing tissue of the embryo. 



Cane sugar in the leaf has been indicated as the im- 

 mediate forerunner of the starch deposited in the chloro- 

 plastids. Aime Girard (^y) has shown that the formation 

 of starch in the tuber of the potato is dependent on the 

 previous existence of cane sugar in the juices of the plant. 

 Lepley (38) has shown that the starch of the maize is 

 dependent on the same appearance ; and Balland (39) 

 has demonstrated the same thing in the case of wheat. 

 Brown and Morris have satisfied themselves that cane suear 

 forms a large proportion of the sugars existing in the sap 

 of the plant of barley during the various stages of its growth, 

 and that this cane sugar disappears pari passu with the 

 formation and accumulation of starch in the seed. 



