Thallophyta and Bryophyta 155 



'f^B^'*' mP^ 









Fig. 14.2— Portion of pustule of Cystopus candidus on stem of Capsclla, Ciaf 0.30- 



1.0-10.0, acetone-tertiary butyl alcohol. 



Safranin-fast green and hemalum-safranin are both excellent 

 combinations for elementary use, and iron hematoxylin is a good 

 nuclear stain (Fig. 14.2) . Mature oospores are abundant in the older, 

 hypertrophied stems and fruits of the host, therefore, a more vigorous 

 kiUing Ikiid is needed; FAA and standard Nawaschin are both 

 satisfactory. As might be expected, the host cells are in a distorted 

 condition at this stage. 



Peronospora parasitica, a common parasite on crucifers, yields 

 excellent preparations by the methods described for Albugo. The best 

 compromise fluid for preserving both the host cells and the fungus is 

 Craf II. Safranin-fast green differentiates the nuclei of the fungus, 

 but not so sharply as iron hematoxylin. 



ASCOMYCETES 



The mold members of this group, such as Aspergillus and 

 Penicillium, are so easy to culture and study from wet mounts that 

 permanent slides are seldom necessary. Permanent slides can be made 

 bv the common whole-mount methods. Such slides are useful for 



