510 MINNESOTA BOTANICAL STUDIES. 



In the exposure of chlorophyll bearing organs of the plants 

 to atmospheres with increased carbon dioxide content, it was 

 found that in all proportions below 25 per cent, the mesophyll 

 cells and guard cells of the stomata contained an unusually 

 large amount of some substance reacting reddish brown with 

 potassium- iodide-iodine, and by farther exposure the chloro- 

 plasts became distended and filled with apparently solid masses 

 of similar substance. Similar formations were to be seen in 

 the leucoplasts of the parenchyma, lateral to the mestome 

 areas in the stems. Effects similar to the above were also se- 

 cured by placing excised leaves in 5-10 per cent, sugar solu 

 tions for 40 hours and the general results in no wise differ 

 materially from those reached by exposure of plants to max- 

 imum insolation. In stems which had lain in a 5 per cent, solu- 

 tion for a week, the parenchymatous elements in immediate 

 contact with the bundles held large amounts of granules which 

 on treatment with potassium hydrate and iodine gave a dingy 

 purple color; in 20 per cent, solution one week a small num- 

 ber of solid i'ed bodies in the mesophyll of stem with iodine so- 

 lution. In tubers placed in the 5 per cent, solution for a 

 week, granules were formed which in every way reacted and 

 had the appearance of those regularly appearing at the be- 

 ginning of the vegetative season. In the JO per cent, solu- 

 tion the formation of granules was not more marked than in 

 the 5 per cent, solution. Prom 5 to 10 per cent, was the most 

 favorable concentration for the formation of starch from sugar. 



In tubers which had lain in 5 per cent, solution of cane sugar 

 10 days the number and size of the leucoplasts and of red 

 starch granules had increased while the nuclei were almost 

 double their former size. Not only were the leucoplasts con- 

 taining red starch found plentifully in the parenchymatous 

 cells and the meristem rays, but also in all but the outer layer 

 ot the cortex as well as the endodermis. In one instance four 

 small granules of similar reaction were unmistakably seen in 

 the nucleus impinging on the nucleolus. A tuber which had 

 lain in a ten per cent, solution of glycerine 50 hours had formed 

 a large number of red starch granules in the parenchymatous 

 cells. It had not effected any changes in a stem in 70 hours 

 however. 



In order to test the effect of calcium and potassium salts on 

 the translocation and condensation of the carbohydrates tubers 

 with one end cut away were placed in the nitrates of these sub- 

 stances in solution, which contained in one instance 1 per cent. 



