MacDougal: tubers of isopyrum biternatum. 507 



and might account for the turgidity of the parenchyma and 

 consequent plumpness of the tubers even when devoid of stored 

 sugars. In tubers taken from plants in the open from May to 

 August many of the leucoplasts surrounding the nuclei in the 

 storage cells as "well as in the cortex contained a simple poly- 

 hedral or globoid granule, which gave reactions similar to the 

 "red starch" of Niigeli which has recently been so thoroughly 

 exploited by A. Meyer (X). The formation of granules in the 

 leucoplasts occurred in plants in the open air in the spring in 

 about sixty days from the beginning of the vegetative season 

 and the expansion of the chlorophyll area. Plants taken from 

 the soil September 31st and placed in a green house at a tem- 

 perature from 15° to 28° C, soon awakened from their dormant 

 condition, began the expansion of the chlorophyll bearing 

 area, and forty days later the formation of reproductive bodies 

 and fifty days later granules appeared in the tubers. In the 

 latter instance the plant had received an amount of illumination 

 about equal in value to that of the first, and perhaps a greater 

 number of heat units. Freshly cut sections placed in iodine 

 water gave the granules a light dingy blue, slightly tinged with 

 brown. Other sections allowed to remain 15 hours in the solu- 

 tion gave a deeper shade of the same tints. In either case they 

 faded if allowed to remain in distilled water after washing. On 

 the addition of dilute chlor-zinc iodine to a section the granules 

 became first a decided blue, passing gradually into a brown and 

 finally into a reddish brown, which gradually faded if the iodine 

 were washed out with water. Treatment of sections left in 

 diastase for 24 hours resulted in the corrosion and almost total 

 disintegration of the granules, but a large number of the cells 

 of the cortex and parenchyma were filled with masses coloring 

 reddish violet on the addition of potassium iodide-iodine, which 

 by A. Meyer's interpretation indicates the presence of a rem- 

 nant of the granules consisting of a amylose and amylodextrin. 

 On treatment with boiling water for a few seconds the gran- 

 ules were swollen, the outer skeleton was distinctly visible and 

 remained unstained on the addition of potassium-iodide-iodine, 

 while a portion of the inner mass was dissolved away. On 

 lengthened treatment with boiling water to 100 seconds the 

 entire granule was disintegrated, inclusive of the colorless 

 skeleton. The granules remained unchanged during several 

 days exposure to cold alkalies but were quickly broken down 

 if the solution were raised to 100° C. On saturation with sul- 

 phuric acid and subsequent treatment with iodine a blue color 



