66 THE SAPROLEGNIACEAE 



Saprolegnia asterophom be transferred to haemoglobin, o.i% or 0.05%, 

 no oogonia are produced; only a vigorous growth results, though Sapro- 

 legnia ferax will have many after being in o.05</o solution for three days. 

 In 0.01% Saprolegnia asterophora produces a few oogonia after four days but 

 not nearly so many as are produced in water in the same time. The ex- 

 planation for this is merely that Saprolegnia asterophora does not need so 

 much food for growth as Saprolegnia ferax does, and that therefore the small 

 amount of food in 0.05% haemoglobin is enough for vigorous growth and as 

 long as there is food enough for \-igorous growth no oogonia will be produced. 

 If 0.05% of total salts KH^PO,, MgSO,, and KNO3 in equal parts be 

 added to the 0.01% haemoglobin no oogonia are produced, but in 0.01% 

 haemoglobin and 0.01% salts a few are found after four days. 



" It is of interest to add that Aclilya racemosa which resembles 

 Saprolegnia asterophora in the number of oospores and in the position 

 of the antheridia, and which is sometimes slightly spiny, will also pro- 

 duce oogonia in water." 



The ease with which the number of antheridia can be made to vary 

 would make this a favorable species for experiment on the causes for 

 such variation. DeBary has noted that in Saprolegnia asterophora 

 oogonia without antheridia appear when the growth is old, /'. e., poorly 

 nourished (on insects). 



The production of sporangia is erratic, always limited, and often 

 entirely suppressed, even for long intervals on different media. In our 

 1922 collection no sporangia ever appeared, although cultivation was 

 continued on various insects and vegetable media for several months. 



Among many cultures made from No. 4 of February 14, 1918, we 

 note the following: 



On corn meal agar. Growth slower than any other Saprolegnia on agar, but threads are 

 thick in the agar and rather stout; no sporangia, but a few oogonia produced after 

 the culture was several days old. Repeated: no sporangia; oogonia formed in abun- 

 dance; a good many antheridia. 

 On pieces of boiled corn. Growth vigorous. Sporangia produced but not in abundance; 



a considerable number of oogonia, about half of which had antheridia. 

 At low temperature. Three young cultures on grubs put in ice box. Growth about 

 as usual; very few sporangia in any one culture; oogonia scattered and very few 

 antheridia present. 



