538 
ADRIAN J. PIETERS 
From Set VIII 
Peptone and levulose 42, 84, 97, 87, 120, 72, 135, 150, 209, 191 — Ave. 118.7 
The advantage of this method Hes in the fact that the mycehum 
studied is practically all in one plane of focus, only a slight tuin of the 
focusing screw being required to enable the observer to count every 
oogonium. That such counting of oogonia was extremely tedious 
and time consuming is quite obvious; consequently the quicker method 
of Klebs was also used. In the following tables wherever the Roman 
numerals are used they should be interpreted as follows : 
I. A fair number, about a dozen in the field of a Leitz number two 
objective. 
II. Many, at least four or five times as many as I. 
III. Very many, at least twice as many as II. 
To express intermediate gradations, the following have been used: 
o-I, a few in each field; I-II and II-III to indicate numbers not 
properly expressible by either figure alone. 
Transferring the mycelium. — In each set of experiments the my- 
celium was removed from some flasks five to six days after inoculation, 
washed, cut up and transferred to haemoglobin for the production of 
oogonia, or to some other solution as will be indicated in the proper 
place. The mycelium in the duplicate flasks was allowed to grow for 
some time longer and was then washed, dried at 100 degrees and 
weighed. The length of time the fungus was allowed to grow before 
being weighed was, of course, precisely the same for every lot of a 
series; with the exception of series I this time was thirty days. The 
capsules containing the haemoglobin or other solution were always in 
duplicate, and sometimes in quadruplicate, and were kept at a temper- 
ature as nearly uniform as possible. This varied roughly between 
13 and 20 degrees, the extremes being only occasionally reached; 
usually the temperature was between 15 and 18 degrees. The first 
experiments were made at Heidelberg and the mycelium was not 
weighed, nor were the oogonia counted. The later experiments were 
made at Ann Arbor. 
Klebs showed that the most important condition for the production 
of oogonia by S. mixta was a gradual decrease in the food supply and 
that for the formation of sporangia a sudden, or at least a rather rapid 
decrease in the concentration of the food, was necessary. To secure 
oogonia, then, the mycelium must be placed in such an environment 
