115 



ing have boon, first, unfavorable climatic conditions; second, imperfect methods 

 of ex tract ing the sugar; third, improper treatment of the '\t radeil juice ; fourth, va- 

 riations and rapid changes in the sucrose of the juice. All of these problems have 

 been successfully solved save the last. It is proper to say, however, that certain 

 methods of cultivation and certain methods of selecting seeds tend to produce maxi- 

 mum contents of sucrose in the cane, and these methods are not yet fully developed. 

 A proper conception of the variations to which the sucrose in sorghum i8 obnoxious 

 can not be had unless we study briefly the method of its formation, how it is stored, 

 and the physiological functions in which it takes part. 



Vegetable physiologists have taught us that a carbohydrate can bo formed by a 

 certain retrogressive change in protoplasm, by which the cell envelope, in other words 

 cellulose, is produced. The carbohydrates which appear in the embryo of a plant are 

 developed at the expense of the stores of material in the seed. After the appear- 

 ance of the chlorophyll cells in the plant the production of carbohydrates takes place 

 with their aid, CO^ being absorbed from the air and free oxygen being eliminated. 



It would be easy to explain the production of carbohydrates by supposing that the 

 chlorophyll cell exerted a reducing influence 1 on the COj which, with the assimila- 

 tion of water, produced, for instance, starch by the formula 6CO_>+5H 2 O CeHioOs -f- On. 

 In the vast majority of plants it is found, in corroboration of this supposition, that 

 the volume of the oxygen set free is sensibly the same as the carbonic dioxide ab- 

 sorbed. The carbohydrate which is generally formed in the chlorophyll cells is 

 starch. This starch is removed from the leaf, and it is supposed that the carbohy- 

 drates which are formed in all parts of the plant are derived from this original sub- 

 stance. 



In point of fact, however, the production of organic matter in a plant does not 

 probably take place in the simple manner above described. It is more likely that 

 the presence of a nitrogenous body is necessary and this proteid itself is the active 

 principle in the production of new organic matter, by a certain decomposition it 

 suffers, with the help of carbonic dioxide and water. Nor is it by any means certain 

 that starch is the only organic matter formed by the chlorophyll cells; in fact, it is 

 known that oil is often the product of this constructive and destructive metabolism. 



But it seems reasonable to suppose that the different sugars are as likely to be formed 

 in the lea'f of the plant as starch. 2 When we remember how easily starch is detected 

 in most minute quantities, and how easily sugar is missed even when present in much 

 larger quantities, we do not wonder that vegetable physiologists have supposed that 

 starch is the first carbohydrate formed in the leaf, and that all the others are derived 

 therefrom. The explanation, which is made of the translation of the starch from the 

 point of its formation to the localities where it is stored, is as follows : 



Take, for instance, the formation of starch in the germ of cereals. We are taught 

 that the starch first formed in the leaves is changed into sugar, and in this soluble 

 state carried through the plant until it reaches the seed. This sugar, reaching the 

 point where the seed is forming, is changed to starch again by the amyloplast. 



Let us subject this theory of the translation of starch to a brief examination. There 

 are two only known methods by which starch can bo converted into sugar, viz : First, 

 by the action of certain acids, and second by the action of certain ferments. The 

 conversion of starch into sugar by acids even at a high temperature and with the 

 stronger acids is very slow. It is simply incredible that such a conversion can take 

 place at the ordinary temperature in the leaf of a plant, and by reason of the action 

 of the extremely dilute weak vegetable acids which the ieaf contains. In the same 



1 It has lately been stated that this reduction is due to the action of electricity on 

 the leaf producing hydrogen and this hydrogen is the active principle in the reduc- 

 tion of the carbonic dioxide. This statement appears to be purely theoretical. 



-'M:\yer ( I'.ot a u ische /eitmig, H, Nos. 5,6,7, 8) has lately shown that the leaf of 

 the plant i incapable of forming starch out of sucrose, laivnlose, etc.. and calls es- 

 pecial attention to the fact that starch may not be the original substance formed. 



