Seaver: Studies in Pyrophilous Fungi 137 



The rapidity of growth, together with the fact that the sex 

 organs in Pyronema are the largest known among the ascomy- 

 cetes, should render the species of this genus of unusual interest 

 to instructors who desire such material for study in the class- 

 room, when the ease with which they may be artificially cultivated 

 becomes known. The length of time during which the spores and 

 mycelium will keep their vitality in the laboratory is a question 

 which time alone will answer. When once the plant is started 

 it can be cultivated generation after generation with perfect suc- 

 cess, enabling the student to trace every step in the life-history of 

 the plant from the germination of the spores to the production of 

 the sex organs and, a few days later, the mature ascocarps. 



The existence of sex organs in this plant has been known for 

 many years, but it is only recently that Dr. R. A. Harper has 

 demonstrated that these are actually functional. His study, how- 

 ever, was based on material collected under natural conditions, 

 he having made no attempt to cultivate the species on nutrient 

 media. The fact that this can be done would render the species 

 as available for regular laboratory study as are the reproductive 

 organs of some of the common algae. 



If it is desired to study the reproductive organs from gross 

 material, and agar is available, this is one of the best media to 

 use, since the development of the plant can be studied in culture 

 from day to day by placing it under the low power of a compound 

 microscope. The surface of the agar is smooth and transparent, 

 so that we may detect the earliest appearance of the forming fruit 

 and these may be mounted on a slide in a drop of agar, thus elimi- 

 nating grit and sand which might be present in material grown on 

 soil. Much care must be taken to get the plants at a very early 

 stage, for immediately after fertilization each cluster of sex 

 organs is surrounded by the tissues of the developing ascocarp, 

 which obscure the details of the reproductive organs. 



Soil which has been heated to a high temperature is apparently 

 more favorable for the production of the sex organs and asco- 

 carps in large numbers than agar. In a pot of sterilized soil the 

 fruit is produced on the pot as well as on the soil and can quite 

 easily be removed for study. Since soil is always available and 

 most nearly approaches the natural conditions for the growth of 



