216 
METHODS IN PLANT HISTOLOGY 
ASCOMYCETES 
This group, popularly known as the “sac fungi,” contains an 
immense number of saprophytic and parasitic forms. The green 
mold on cheese and leather, the leaf curl of peach, the black knot of 
cherry and plum, and the powdery mildews are familiar to everyone. 
The few objects selected will enable the student to experiment, but he 
must not be discouraged if success does not 
crown the first attempt, for some members 
of the group present real difficulties. 
Peziza.—The Pezizas and related forms 
are fleshy, and present but little difficulty 
in fixing, cutting, or staining. They are 
abundant in moist places, on decaying 
wood, or on the ground. The apothecia 
have the form of little cups, which are 
sometimes black and sometimes flesh- 
colored, but often orange, red, or green. 
For general morphological work it is 
better to tease out fresh or preserved 
material. Such views as that shown in 
Figure 56 are easily obtained in this way. 
For permanent preparations showing such 
views, it is better to stain in bulk in alum 
carmine or in Delafield’s haematoxylin, 
and then tease out the asci in glycerin 
or balsam. Sections showing the entire 
ascus should be 10 to 15 n, in thickness. 
For the free nuclear division in the 
ascus, and also for the development of the 
ascospores, Flemming’s weaker solution, 
followed by the safranin, gentian-violet, 
orange combination has given excellent results. The centrosomes, 
especially at the first division in the ascus, are sharply defined and 
the radiations are conspicuous. With iron-alum haematoxylin and 
orange, the nuclear detail and the centrosomes are better, but the 
spindle and radiations are not so sharply defined. For such details, 
sections should not be thicker than 5 and 3 m will give a clearer view. 
Morchella esculenta is very good for the development of the ascus 
because the nuclei are very large. 
Fig. 56 .—Peziza odorata: three 
asci and many paraphyses; fixed 
in corrosive sublimate, stained in 
bulk in alum carmine, teased out, 
and mounted in balsam. X245. 
