SINIGRIN 245 



amount of glucosides in the bark and other parts of plants at 

 different seasons of the year. Thus in Salix and Populus the 

 glucoside (sahcin) is most abundant in the autumn and winter, 

 and is used up in the following spring during the period of 

 flowering and seed formation ; also in the case of Taxus the 

 glucoside (taxicatin), which appears principally in the young 

 shoots, is greatest in amount in the autumn and winter. In 

 Panghim ediile and other plants the amount of cyanogenetic 

 glucosides is greatest in young leaves, with increasing age the 

 amount diminishes. 



Guignard * does not beheve that glucosides, or at any rate 

 the cyanogenetic ones, are reserve food-stuffs, since, if in- 

 troduced into the food-materials of a plant, glucosides have 

 an injurious effect, owing to the aromatic residues. 



Combes, t however, finds that a glucoside is toxic only to 

 plants in which it does not naturally occur ; he thinks that 

 glucosides do not furnish carbohydrate food, since plants 

 grown in an atmosphere free from carbon dioxide are unable 

 to make use of these substances. 



Peche X holds that hydrocyanic acid is a direct product of 

 photosynthesis ; some of it combines with sugar to form a 

 glucoside, and some is transported in a labile form, probably 

 in a loose combination with tannin, and stored for future use 

 as food in various tissues. * 



The occurrence of certain glucosides, especially in places 

 of active metabolism such as leaves and young shoots, may 

 indicate that certain bye-products are fixed, either temporarily 

 or more permanently, in this form. 



The exigencies of space will permit of reference only to the 

 following examples, which are among the more important and 

 more interesting of the glucosides. 



SINIGRIN. 



Sinigrin, or myronate of potash, occurs in the seeds of 

 certain Cruciferse, notably Sinapis nigra. It is split by the 



* Guignard : " Compt. rend.," 1905, 141, 236 ; 1906, 143, 451. 



t Combes : " Rev. gen. Bot.," 1918, 30, 216. 



X Peche : " Sitz. Kais. Akad. Vienna," 1912, 121, 33. 



