306 BOTANICAL GAZETTE [ocroser 
infusions of bean stems or mushrooms in Petri dishes. In these 
dishes had been placed carefully sterilized glass slips and cover- 
slips. The spores germinated sometimes upon the slips, some- 
times floating free in the liquid, in which case the colonies 
rested upon the surface. Where they germinated on the slips, 
the mycelium adhered closely to the glass and made the process 
of fixing and staining much less difficult. On the other hand, 
the colonies which floated on the surface of the liquid seemed 
to take on more natural characteristics and they could be lifted 
out ona slide and prepared for the microscope. Many of the. 
colonies thus grown developed mycelium in such abundance as 
to make observation very difficult. This was especially true of 
colonies grown in mushroom infusion, which seemed a most 
favorable medium, but it was also true that in these dense 
colonies the fruit was most abundant. The material for section- 
ing was grown in potato agar slightly acidulated to suppres 
bacteria. 
Fixing and staining.—Slides bearing colonies were lifted cate 
fully from the Petri dishes at different stages in their develop- 
ment and washed in water. Various methods of fixing and 
staining were tried. The most satisfactory was to fix with a 
cold I per cent. acetic saturate solution of mercuric chloride, 
stain with alum-eosin and mount in glycerine. The mercuric 
chloride fixes this material almost instantly and when washed 
off well with water leaves it in condition to take a clear decisive 
stain in the alum-eosin. This stain does not bring out nucleat 
structures with great distinctness, but cell walls come out sharp 
and clear. It stains the young mycelium and perithecia almost 
instantly, the latter taking a slightly deeper stain than the for 
mer. Good results were also obtained by staining with cari 
alum the material fixed in this way. Ehrlich-Biondi, haematy : 
lin and fuchsin were also found fairly good. The efficiency ° 
any stain was found to depend largely upon the age of ise 
fungus. Young mycelial threads stain very readily, while t° 
very mature ones refused the stain altogether. os 
Sectioning —Small blocks of potato agar con 
taining colo- 
