[Vol. 6 

 224 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



it to be present in the tubers during growth, and also detected 

 its presence in oats, wheat, maize, and rice during germination. 

 They were the first investigators to prepare the enzyme from 

 the extracts of germinated grain, extracting the latter with water 

 and precipitating the ferment by means of alcohol. To this 

 alcoholic precipitate they applied the term diastase, which has 

 persisted since that time. Subsequent investigation showed 

 diastase to be present not only in tissues in which starch normally 

 occurs as a storage product, but also in some where the reserve 

 materials are stored as sugar. Thus, in 1878, Baranetzky found 

 diastase present in the roots of carrots and turnips, which con- 

 tain no starch. He also found it in the leaves and stems of several 

 plants and in potato tubers. From this evidence, he suggested 

 that diastase was probably universally present in living cells, 

 and later work has practically confirmed this opinion. 



Miiller-Thurgau ('82) showed that under certain conditions 

 the amount of cupric-reducing substances in leaves increased at 

 the expense of the starch present. He also found ('85) that 

 exposure of potato tubers to a temperature of 0° C. for a month 

 resulted in an accumulation of sugars, with a corresponding 

 loss of starch. Contrary to popular opinion, it was determined 

 by him that no sugar was formed in potatoes which were actually 

 frozen. He has also found that when potatoes which had be- 

 come sweet by exposure to low temperatures were placed at a 

 temperature of 8-10° C. the sugar disappeared. Miiller-Thurgau 

 considered these phenomena to be due to an enzymic process, 

 which, while more rapid at high temperatures, occurs also at low 

 temperatures. According to his ideas, the lessened respiration 

 at low temperatures, entailing the use of less sugar, together with 

 an inhibition of re-formation of starch from sugar — which 

 re-formation takes place rapidly at high temperatures — allows 

 the sugars to accumulate when potatoes are kept at 0° C. 



Brasse ('84) is considered by Brown and Morris ('93) to have 

 been the first to prove conclusively the presence of diastase in 

 leaves. He examined the leaves of the potato, dahlia, beet, 

 tobacco, and some other plants, and measured the rate of the 

 activity of the diastase obtained from extracts by precipitation 

 with alcohol. This product w^as allowed to act upon starch 



