MacDougal: tubers of isopyrum biternatum. 505 



ditions was used, but since the latter date I have had an ample 

 supply of material under constant observation in the plant 

 houses. 



In the determination of the contents of the storage cells of 

 the tuber the following reactions were obtained from Septem- 

 ber to May— during the winter resting period of plants under 

 natural conditions. 



If sections of a tuber freshly detached from the plant were 

 mounted in a drop of strong alcohol, the parenchyma cells were 

 almost instantly filled with numerous small globules which ap- 

 peared pale gray tinged with violet. An immense number of 

 these globules might also be observed in the fluid surrounding 

 the sections. If a drop of water were placed at the edge of 

 the cover glass the globules instantly disappeared, and ii the 

 slide were allowed to remain in the open air a few hours the 

 water absorbed from the air and extracted from the walls was 

 sufficient to dilute the alcohol to such a point that the globules 

 were dissolved. A series of tests with a number of solutions 

 of alcohol revealed the fact that the globules were formed as 

 above with all solutions of alcohol above 80 per cent, by volume 

 but with the use of a 75 per cent, solution the globules were 

 not formed so quickly and were redissolved in a few minutes. 

 With 70 and 65 per cent, solutions the globules were slowly 

 formed to disappear soon by an instantaneous breaking down. 

 In a 60 per cent, solution no globules were formed. This 

 globular formation on the addition of strong alcohol was first 

 described by Kraus (VI) as seen in the sugar beet and was sup- 

 posed by him to be indicative of the presence of sucrose; but it 

 is possible that the globules might consist partially of reffinose 

 or secalose (XIII). If the sugar laden cells were kept under 

 observation when the drop of alcohol was allowed to act from 

 one side, the globules might be seen forming against the cell 

 wall through which the alcohol entered and being carried with 

 the current toward the center of the cell, where the first ones 

 were dissolved owing to the great proportion of water present 

 here. With the saturation of the cell sap with alcohol, the 

 sugar was again thrown down and finally the cells would be 

 almost entirely filled with the globules which reached a size 

 equal to one-tenth the diameter of the cell or were barely 

 visible points (Fig. 4, PL 29). In Kraus' reactions the 

 globules were seen to disappear briefly, doubtless owing to the 

 gradual dilution of the alcohol as above described. In the 

 material under examination, however, if the alcohol were re- 



