528 MINNESOTA BOTANICAL STUDIES. 
of a young tuber is diagrammatically shown in Fig. 11. The 
cell contents of the hyphe of the tuber respond very neatly to 
a test for glycogen given by Dr. L. Errera,* and it seems very 
probable that this substance is a very large, if not the chief 
constituent of the cells. Errera’s test is made with a reagent 
composed of 450 parts of water, three parts of KI and one 
part of iodine, and he designates it as ‘‘ solution Iodée au 74,5.” 
According to him, material possessing glycogen when stained 
in this solution or when mounted in a drop of it takes on a red- 
dish brown color, which disappears in a temperature of 50—60° 
C., but returns upon recooling. Some of the tests made on 
Dictyophora tubers were with material taken from 70 per cent. 
alcohol sectioned, transferred to water and mounted directly in 
a drop of the reagent. 
In other instances sections that had been machine cut, stained 
in Bismarck brown, and mounted in Canada balsam were soaked 
in xylol to remove the cover glass and balsam, carried through 
alcohol to water, stained for a moment in Errera’s mixture, and 
then mounted in water. In every case the reaction was sharp 
in all particulars. 
Assuming that Errera’s test is a correct one, and there ap- 
pears no good reason for doubting it, it is evident that a large 
portion at least of the cell contents of the tuber is glycogen. 
Zopf, Burt t and others have associated the presence of gly- 
cogen in fungi with the immediate need of the plant for rapid 
growth, but there is at least a possibility that this reserve food 
supply in the tuber is in some way connected with the economy 
of the plant in reproducing itself vegetatively the following 
season. Or it may be that there exists a direct connection be- 
tween the tuber and the rapidly developing sporophore, though 
there is no evidence that any of the supply of glycogen has been 
exhausted from any of the tubers collected or found upon the 
vegetative tract. If it is found upon further investigation that 
these tubers are connected with vegetative reproduction and 
that by means of them it is possible to artificially propagate the 
plant, it will be of great advantage in the study of the younger 
stages of development of the reproductive area. Hitherto the 
rare occurrence of the plant and its allies has made the study 
extremely difficult. 
* Leo Errera, Sur le Glycogéne ches les Basidiomycetes, 1885. 
+ Bot. Gaz. 24: 18097. 
