RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 539 
that, while no rapid growth takes place, the formation of sporangia 
shall be almo^^ or entirely prevented. It is evident that a mycelium, 
exhausted by the formation of sporangia, cannot produce the number 
of oogonia that it could have produced under other conditions. Hae- 
moglobin, in concentrations to suit, offers such a medium, but un- 
fortunately the commercial article is not of uniform purity, always 
leaving more or less of an insoluble precipitate. Klebs ('99, p. 520) 
states that in 0.05 percent haemoglobin only vegetative growth took 
place and that even in o.oi percent sporangia were but sparingly 
produced. The forms of S. mixta collected by the writer formed 
sporangia readily in 0.05 percent haemoglobin and some even in 
0.075 percent, and this was also true of S. ferax and of 5. monoica. 
While Klebs's form may have developed sporangia less readily than 
those which the writer used, the difference in the results is doubtless 
due largely to the relative purity of the haemoglobin. As a conse- 
quence concentrations thought to be the same are not always so, and, 
owing to the delicate balance between growth and sporangia forma- 
tion existing in a weak solution, a slight difference may result, either 
in the formation of many sporangia, and in the consequent weakening 
of the mycelium, or in an undue amount of growth with the attendant 
formation of the poisonous products of metabolism. In either case 
the formation of oogonia will be interfered with. 
Purified water. — The earliest tests made in Heidelberg brought 
out the fact that distilled water from the chemical laboratory had a 
harmful effect on the mycelium. Horn ('04) had already observed 
this and had attributed it to the presence of copper, or of some other 
metal in the water. He found that when common distilled water was 
re-distilled out of hard Jena glass, it lost its poisonous properties.. 
This was not found to be so in the present case. Distilled water 
was twice re-distilled out of hard Jena glass, but, although the latter 
was better than the distilled water as it was received from the chemical 
laboratory, it was by no means as good as freshly collected rain water. 
The action of the distilled water was not uniform, sometimes wholly 
preventing the formation of sporangia, while at other times some 
sporangia were formed but did not discharge normally. This was 
also found to be true sometimes of the rain water, which, though often 
satisfactory, was not infrequently quite as toxic as the distilled water. 
Much of the work first done had to be discarded because of this un- 
reliable action of the water. The use of carbon black as described by 
