92 



THE SAPROLEGNIACEAE 



completely to cover the oogonia, short, club-shaped, or often tuberous and 

 branched, terminating slender branches of diclinous or rarely androg- 

 ynous origin which at times show a tendency to twine about the oogonial 

 branches; antheridial tubes enter the oogonia, run among the eggs, and 

 probably fertilize them. 



Found 35 times in branches, marsh borders, etc., often with algae, 

 such as Vaucheria, as in brook near east gate of the University campus, 

 Arboretum branch, etc. 



In fig. I the sporangia are shown in a group, after the manner of 

 Achlya. The bending of the sporangia that is quite noticeable in this 

 figure is characteristic, though not always so pronounced. 



In figs. 2 and 3 are shown the proliferation of sporangia by both 

 the Achlya and Saprolegnia methods on the same thread. The latter 

 method is rare.* 



The behavior of the spores on emerging is remarkable and very 

 variable. The usual behavior is for some of the spores, perhaps a half 

 or a third, to swim slowly away on emerging, the others remaining attached 

 to the sporangium mouth and encysting there. In regard to their action 

 we give the following quotation somewhat modified from notes in Mycologia 

 (1. c, p. 286) made at the moment of observation: 



The spores emerge somewhat elongated and may be seen to bend backward at the 

 ends and fuse into a pear-shaped spore, as is the case in Leptolegitia. The spores as a rule 

 move sluggishly and most of them soon settle to the bottom near the sporangium mouth and 

 encyst, also a lot of inactive ones are often left in a group that sticks to the sporangium 

 mouth, giving the effect of Achlya. 



We find cases where all, or nearly all, of the spores group themselves at the mouth 

 exactly as is typical of Acldya. When conditions are unfavorable the spores sometimes 

 do not emerge at all and in such cases they sprout in position. 



Noticed two sporangia empty near together. In one the spores grouped themselves 

 at the mouth of the sporangium just as in Achlya, except that a few of the outermost gently 

 rocked themselves away a little distance from the main mass and then settled down. The 

 spores that remained in a mass at the tip of the sporangium also showed a very slight rock- 

 ing movement, thus proving the presence of cilia, but in a couple of minutes they became 

 quite still. In the other sporangium the spores charged out with great rapidity and every 

 one dashed rapidly away. 



A sporangium emptied and all the spores sank slowly to the bottom of the 

 dish, separating themselves considerably by a gentle rocking motion. After settling 

 individuals would move spasmodically at intervals, turning and jerking, but none swam 

 actively or any distance. This interrupted mo\ement continued for at least a half hour 

 after emergence. 



A sporangium emptied (temperature 89° F.) and all the spores were expelled to some 

 distance from the opening, all remaining in a group as if held lightly together, and all 



*We know of no reference in the literature to internal proliferation of any kind in Achlya, 

 except by Petersen (Ann. Mycologici 8: 520. 1910), who says: "Thus I have seen zoospor- 

 angia which had proliferated in undoubted species of Achlya." We have found such prolif- 

 eration twice in A. imperfecta. 



