508 MINNESOTA BOTANICAL STUDIES. 



resulted. In cells containing the "red starch" granules a cop- 

 per reducing substance — a carbohydrate — is to be found during 

 the entire year. 



The mesophyll cells of the leaves after a period of activity 

 of the chlorophyll, contained a substance, which by its reac- 

 tion to iodine, must have consisted largely of amylodextrin, 

 and during the period of maximum activity, solid masses were 

 to be found in the leucoplasts similar to those in the tubers. 

 Only in such instance was a copper reducing sugar found and 

 in small quantity in the mesophyll cells. It would appear by 

 inference that the ultimate product of the synthetic process in 

 the mesophyll is sucrose, that the surplus supply is converted 

 into a starch different only from the ordinary forms by the 

 proportions of a amylose and B amylose, and that the form 

 taken in translocation is probably maltose, or some copper re- 

 ducing sugar since this form was present from the leaves to 

 the tubers and in greatest quantity in the conducting cells. 

 This is further confirmed by the fact that in detached por- 

 tions of rhizomes and tubers the amount of copper reducing 

 sugar was sensibly diminished and as the amount of cane sugar 

 increased. The same was also true of tubers placed in a 5 per 

 cent, solution of cane sugar. 



A similar scarcity of copper reducing sugar was noted in 

 tubers in which the formation of red starch granules was be- 

 gun. As for the physiological conditions which lead to the 

 condensation of the sugars into starch granules containing 

 large proportions of amylodextrin and in consequence reac- 

 ting reddish brown to iodine, nothing exact can be given. Since 

 the amylodextrin is formed from amylose by diastatic action 

 it seems entirely possible that such starch granules indicate a 

 constant and strong action of the ferment during the process 

 of condensation, a view confirmed by the constant presence, 

 during both the resting and actively vegetative period, of large 

 proportions of a diastatic ferment in the storage cells. 



When sections of a tuber were mounted in water and a cry- 

 stal of ammonium tartrate placed at the edge of the cover and 

 allowed to dissolve there were formed large globules nearly 

 filling the parenchymatous cell cavities. When fresh sections 

 of the tuber were placed in alcohol-tartaric acid solution, a 

 globular aggregation of granular or radial structure was formed 

 in the perfect cells, but in those which had been mechanically 

 torn or injured, a number of crystals of rhombic form of the 

 hexagonal system with angles, incomplete or obscure. In a 



