512 MINNESOTA BOTANICAL STUDIES. 



masses or octahedral or needle shaped crystals all of which 

 appear black in transmitted light. 



If epidermal sections of the leaves were placed in a solution 

 of 1 part tartaric acid in 20 parts absolute alcohol for two hours, 

 there appeared inside the cells a number of globular aggrega- 

 tions of a granular or in some cases radial structure. Later in 

 some of the cells these were broken up and were replaced by 

 radially arranged bundles of crystals similar to those in the 

 tuber which were not dissolved in 95 per cent, alcohol in 30* 

 days. When a cell containing these aggregations was dis- 

 turbed by crushing the process was hastened. If untreated 

 sections were placed in a Mayer's solution of potassic- mercuric- 

 iodide, a whitish granular precipitate was formed in the mount, 

 partly inside the cells but for the greater part in the fluid 

 in contact with them, or their inner walls. This precipitate 

 was insoluble in alcohol, and weak and strong hydrochloric 

 acid. A small amount of the potassic-mercuric-iodide precipi- 

 tate was also formed in the outer layers of the cortex in the 

 tubers. 



So far as the above and the reactions with the alkaline car- 

 bonates are capable of interpretation, it would appear that 

 there is present in the sap of the external tissues of the leaves 

 and stems some form of tannin and a chromogen from which 

 the characteristic red color of the leaves may arise. In addi- 

 tion the cells of the outer layers of the cortex of the tubers con- 

 tained one or more pale grayish globules (Fig. 8, PL 29) whose 

 diameter may be nearly equal to that of the cell. They are to 

 be found as well in a large proportion of the cells of the exter- 

 nal tissue in all parts of the root to within 1 or 2 mm. of the 

 tip. These globules are immediately soluble in alcohol, slowly 

 soluble in either, and take on an eosin red coloration on treat- 

 ment of fresh material with chrom-acetic-osmic-acid, finally be- 

 coming black. If sections treated with potassium-iodide-iodine 

 are placed in 95 per cent, alcohol for 48 hours the globules will 

 disappear entirely except at certain places in the outer layer of 

 the cortex where a few retain their form, size and the charact- 

 eristic reddish brown coloration. These globules take on a red 

 color in a solution of alkannin, and appear to belong to the 

 fatty oils. Similar globules are to be found in the outer lay- 

 ers of the tubers of Isopyrum adoxoides. In a number of 

 the outer cells are to be found pale yellowish masses or aggre- 

 gations of rounded granules which are insoluble in cold alcohol 



