218 
Journal of Mycology 
[Vol. 9> 
A NEW METHOD OF MOUNTING SUPERFICIAL 
FUNGI. 
HERBERT H. WHETZEL. 
In Studying Sphseropsis malorum on apple leaves, I found 
that in its early stages, before pycnidia were formed, well defined 
brown spots appeared. Although I examined many sections from 
these brown spots, I failed to discover any mycelium. Material 
scraped from the surface showed nothing of the mycelial char¬ 
acter of the fungus. I had about decided that the spots were not 
due to a fungus when I found a few immature pycnidia on one of 
the spots. It then occurred to me to cook a piece of the leaf in a 
weak solution of Potassium hydrate (KOH) and by macerating 
the leaf tissues thus to discover the mycelium. I had success¬ 
fully used this method in studying mycelium distribution in the 
galls of Gymnosporangium macropus. After slowly cooking the 
leaves for half an hour, I found that the brown coloring of the 
leaves was bleached out. The epidermis separated as a thin sheet 
from the other tissues of the leaf. After washing thoroughly in 
clear water, I examined it under the microscope and found, that, 
while the leaf tissue was entirely bleached, the brown threads of 
the fungus still retained their color and showed beautifully. 
The same method used on several other fungi growing super¬ 
ficially on leaves, stems and fruits has given in every case excel¬ 
lent results. This method has never before been used, so far as 
I know, and believing that other persons may find it helpful, I 
give it in detail as I have worked it out. 
1. Carefully peel or slice off a piece of the epidermis on 
which the fungus is growing. Care should be exercised to take 
away as little subepidermal tissue as possible. 
2. Immerse the slice in a 2-4% solution of Potassium 
hydrate and boil in an evaporating dish over a low flame for 20- 
30 min. Cook long enough to remove all the color from the 
tissue of the host. 
3. Pour off the Potassium hydrate solution and wash by 
letting the material stand for 10-20 min. in each of two or three 
changes of clear water, stirring it about occasionally. If all the 
color is not removed from the host tissue cook again. Carefully 
pick away any pieces of subepidermal tissue that may cling to 
the epidermis. 
4. Dehydrate in 95% alcohol. 
5. Clear in carbol clearer (2 parts pure carbolic acid and 3 
parts turpentine.) 
6. Mount in Canada balsam. 
The Advantages of this method may be summed up as fol¬ 
lows : 
