INTRODUCTION 9 



In botli Sdprolcf^niii and Achlya it frequently hai)pcns that the 

 discharge of tiie sjiores is only partial, a few, or even a good many spores 

 being left in the sporangium. These retained spores may emerge from 

 their cysts, as normally, for a second swimming stage, moving about 

 within the sporangium until they find their way out by its mouth, if 

 they ever do. This is shown by Hildebrand ( '67) for his A chlya polyandm, 

 bv Lechmere ('10) for Saprolegnia tonilosa (?), plates i and 2, figs. 22, 

 23,, 30, 31, also in fig. 2 of his 191 1 paper, and very strikingly in our form 

 of .4. Klebsiana (which see). Lechmere erroneously calls this the Dicty- 

 uchiis type of asexual reproduction. It is doubtful if the sterile species 

 of Saprolegnia (a parasite on fish) studied by him in his first paper is 

 Saprolegnia tonilosa. It is more apt to be our 5. parasitica. 



Another peculiar and rare variation in the behavior of the sporangial 

 contents is described and figured by Horn ('04) in a plant he calls Achlya 

 polyandra deBary (which may be our A. imperfecta). At a temperature of 

 31° to ^2° Celsius, sporangia were formed which emptied large masses 

 of protoplasm through several openings. These masses, then, by direct 

 division formed spores, some of usual size (lOfx), some larger (up to 40^1 

 in diameter). If now brought to room temperature these small spores es- 

 caped from their cysts and swam. The larger ones germinated directly. 

 Horn also mentions the occasional appearance of double spores from nor- 

 mal sporangia. The discharge of large and irregular masses of protoplasm 

 from the sporangia had been figured long ago by Leitgeb ('69), for 

 Saprolegnia monoica as Biplanes. In plate 24, fig. 5 he shows several 

 such masses, some with cilia at difTerent points, also several double 

 zoospores. In Achlya imperfecta from Chapel Hill, I have observed 

 several times the emptying of the entire protoplasm from a sporangium 

 at the tip, the mass falling at once to the bottom as a long contorted 

 rope. This is conclusive evidence that the spores are discharged by 

 internal pressure and not through their own motion. In numerous 

 other species I have seen masses of protoplasm much larger than spores 

 discharged from the sporangium and these may have several sets of cilia 

 (pi. I, fig. 12; pi. 7, fig. i; pi. 39, fig. 4; pi. 60, figs. \2 and 14). 



It will, of course, be understood that the \-ariations reviewed above 

 are in no sense fortuitous or accidental. They are the results of en- 

 vironmental conditions and many of them may now be induced at will 

 by the investigator. 



In this connection I feel it necessary to give a word of caution against 

 the attitude adopted by Lechmere in his two papers in the Xew Phytol- 

 ogist, both of which are referred to above. In the summary of his first 

 paper he says: "As the result of keeping a species of Saprolegnia under 



