338 Harper.—Sexual Reproduction in Pyronema 
the leaves or leaf mould offering little or no resistance to the 
microtome-knife. More trouble is sometimes occasioned by 
diatoms, which were found extremely abundant in the sub¬ 
stratum in some cases, and indicate the degree of moisture 
favoured by the Fungus. Blue-green Algae and some 
Conferva-like filamentous species were also present in many 
cases. Pyronema , as I have found it, is extremely susceptible 
to drought, a short exposure in the laboratory causing it to 
wilt and die. These points as to its occurrence are of interest 
in comparison with Kihlmann’s experience. He seems to 
have found the Fungus abundant in clefts on stones and 
to have secured successive crops of young fruits by wetting 
the stones every three to four days. 
For fixing my material I used Flemming’s solutions, both 
the stronger and weaker, and also of a strength about half 
that of the weaker formula. Hermann’s and Merkel’s solutions 
were also tried. Of the sublimate acetic solutions both 
Kaiser’s and Wilson’s were tried. Merkel’s solution was 
found far superior to all the others as a fixing-agent for the 
younger stages in the development of the fruits, up to the 
time of ascus-formation. Solutions containing osmic acid 
such as Flemming’s solutions in any strength seem to reduce 
the protoplasm, of the oogonium especially, to a dense undif¬ 
ferentiated mass in which even the differential staining of the 
nuclei was a matter of great difficulty. This action of 
the solutions containing osmic acid seems due to the presence 
in the protoplasm of the reproductive cells of certain reserve 
food-materials whose nature I have not attempted as yet to 
more fully determine. As a result of their presence young 
material fixed in Flemming’s solution was practically useless. 
Merkel’s solution, however, gave preparations of a clearness 
which left little to be desired. The sublimate solutions gave 
well-fixed and unshrunken sections which, however, seemed 
not well suited to differential staining with the anilin dyes. 
With iron-haematoxylin this material gave very good figures, 
but the plain black or blue and white is far less useful than 
the series of varied shades which can be obtained with such 
