RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 563 
oogonia was often so irregular that it was not possible to secure a fair 
average. The number of the oogonia was therefore estimated. The 
most important cause of the lack of good results with this species 
is that no entirely satisfactory solution was found to which the my- 
celium could be transferred for the formation of oogonia. Early 
experiments showed that haemoglobin was worthless, oogonia were 
formed but no oospores were ever developed. Many experiments 
were then made with peptone and sugars as suggested by Obel ('lo) 
and also by placing masses of mycelium into pure water or water 
to which salts had been added. 
A. prolifera will form oogonia in water as is the case with A. 
racemosa, but unfortunately the formation of oogonia is prevented by 
a temperature lower than that at which sporangia continue to be freely 
formed. If however a mass of mycelium is left in the water in which 
it was placed on being taken from the culture flask, it may find suf- 
ficient food present to prevent any free formation of sporangia and 
thus permit the production of oogonia. This method was therefore 
used with the others, but the results have not been uniform. Many 
solutions containing peptone and sugars were tried and at tempera- 
tures from 10° to 24° C. A few of the results of these tests are given 
in Table XVIII; it is thought unnecessary to extend the record as in 
most of the other cases only vegetative growth took place with an 
occasional oogonium, sometimes with and sometimes without oospores. 
Oogonia were formed under most of the conditions presented in 
the table but they were seldom well filled, often only a small number 
of the oogonia containing oospores. The failure to produce oospores 
appeared generally to be connected with excessive vegetative growth 
although the specific value of the carbohydrate is clearly seen when 
the record of numbers 3, 4, 6 and 7, each of which contained o.oi 
percent peptone, are compared, or when the record of number 8 is 
compared with that of number 11. Both of these solutions contained 
0.02 percent peptone but when this only was present the fungus 
made a dense growth which rapidly filled the dish and no oogonia 
were produced. The addition of sucrose restricted the growth and 
caused the development of many well filled oogonia In nearly all 
peptone-sucrose solutions oogonia were freely produced; maltose and 
dextrose were also generally satisfactory; levulose always encouraged 
a great growth of delicate hyphae while few oogonia were formed 
and those were usually empty. 
