46 THE SAPROLEGNIACEAE 



6. Saprolegnia mixta deBary. Bot. Zelt. 41: 38 and 54. 1883. 



? S. heterandra Alaurizlo. Jahrb. f. wiss. Bot. 29: 87, pi. i, figs. 



18-27. 1896. 

 ? S. dioica Schroet. Jahrl). d. Schles. Gcscll. f. vaterl. Cultur, 1869, 



47: 143- 1870. 

 As originally defined by deBary this species was placed in the Ferax 

 group and separated from 5. ferax on the one hand by having antheridia 

 on about fifty per cent of the oogonia instead of none or a very few, 

 by the swollen oogonia with fewer eggs, and by the more delicate my- 

 celium; on the other hand it was distinguished from S. monoica by fewer 

 antheridia, more numerous and often larger pits in the oogonia, and 

 by the weaker mycelium. Saprolegnia hypogyna, with very similar oogo- 

 nia, is easily separated from all others by the sub-oogonial cell. 



In recent years there has been great confusion in regard to S. mixta, 

 and subsequent collections have shown pretty clearly that this species 

 and probably also S. ferax are composed of a number of forms, them- 

 selves varialilc, of which deBary had only one. In a very sensible dis- 

 cussion of this subject Pieters (Mycologia 7: 307- 1915) has concluded 

 that from Avhat is known at present it is best to consider as S. mixta 

 those forms with weak mycelium and with antheridia on one-half or 

 more of the oogonia, while to 5. ferax should be referred those with 

 stronger mycelium and only a small number of antheridia on fly cul- 

 tures at a temperature of 12-15 degrees centigrade. Saprolegnia monoica 

 will still include only those forms with antheridia, usually androgynous, 

 on e\ery oogonium in all ordinary natural media. To these conclusions 

 we agree (if 5. mixta is to be retained at all), but it is not to be supposed 

 that this convenient arrangement will put an end to all confusion in so 

 various a set of forms, or that it adequately expresses the complexity of 

 the group. 



To show still further the frail basis on which this species stands 

 we ha\-e but to refer to the most recent monographs of the family by 

 IMinden, who says that "S. mixta would, indeed, have to be united with 

 5. Thiireti \S. ferax] had not deBary asserted its constancy over a long 

 period." (Krypt. H. Mark B. 5: 519. 1912). From our own experience 

 we would not hesitate to reduce S. mixta, and retain it only in deference 

 to the opinion of deBary and Pieters (but see remarks below as to the 

 plant Pieters observed). 



By applying the above rules we find that we have secured several 

 times in Chapel Hill and once in Hartsville, S. C, forms that can be 

 referred to S. mixta. We do not illustrate these forms, as the drawings 

 could not be distinguished from similar ones taken from S. ferax. Of these, 

 No. I of November 2, 1916, may be described as follows: 



