70 HOW CROPS GROW. 



brilliant needles, which yields dextrose and a resin by action of dilute 

 acid, and by oxidation produces vanillin, the flavoring principle of the 

 vanilla bean. 



Mutual Transformations of the CarbJiydrates, — One of 

 the most remarkable facts in the history of this group of 

 bodies is the facility with which its members undergo 

 mutual conversion. Some of these changes have been 

 already noticed, but we may appropriately review them 

 here. 



a. Transformations in the plant. — In germination, the 

 starch which is^largely contained in seeds is converted 

 into amidulin, dextrin, maltose and dextrose. It thus ac- 

 quires solubility, and passes into the embryo to feed the 

 young plant. Here these are again solidified as cellulose, 

 starch, or other organic principle, yielding, in fact, the 

 chief part of the materials for the structure of the seed- 

 ling. 



At spring-time, in cold climates, the. starch stored up 

 over winter in the new wood of many trees, especially the 

 maple, appears to be converted into the sugar which is 

 found so abundantly in the sap, and this sugar, carried 

 upwards to the buds, nourishes the young leaves, and is 

 there transformed into cellulose, and into starch again. 



The sugar-beet root, when healthy, yields a juice con- 

 taining 10 to 14 per cent, of saccharose, and is destitute 

 of starch. Schacht has observed that, in a certain dis- 

 eased state of the beet, its sugar is partially converted 

 into starch, grains of this substance making their appear- 

 ance. {Wilda's CentralMatt, 1863, II, p. 217.) 



In some years the sugar-beet yields a large amount of 

 arabin, in others but little. 



The analysis of the cereal grains sometimes reveals the 

 presence of dextrin, at others of sugar or gum. 



Thus, Stepf found no dextrin, but both gum and sugar In maize-meal 

 (Jour, filr Prakt. Chem., 76, p. 92); while Fresenlus, in » irftre recent 

 analysis ( Vs. St., I, p. 180), obtained dextrin, but neither sugar nor gum. 

 The sample of maize examined by Stepf contained 3.05 p. c. gum and 

 3.71 p. o. sugar ; that analyzed by Fresenlus yielded 2.33 p. c. dextrlji. 



