ACHLYA 103 



more branched, tuberous, antheridia also present at times and arising 

 from the suboogonial cell or below it or even from the main hypha; in 

 the latter case rarely tliclinous. Fertilizing tubes arising through the 

 common septa from the suboogonial cell and penetrating the oogonia 

 from below (hypogynous), also from the other antheridia when present. 



Compared with other species it may be said to have medium occur- 

 rence, appearing mostly in fall in such places as brook south of athletic 

 field. Arboretum branch, branch on south edge of Glen Burnie meadow. 



An extremely variable plant. The smallest or largest oogonia may 

 be quite smooth or heavily spined or with every possible variation be- 

 tween; they may be quite free of antheridial cells or branches or either 

 or both may be present, and all these different conditions may be found 

 in a single culture on ordinary- media, as a mushroom grub or gnat. 



The presence of a hypogynous antheridial cell and the origin of the 

 fertilizing tubes from the septa separating this cell from the oogonium 

 distinguish this from all other species of Saprolegniaceae except the 

 Ilypogytui group in Saprolegnia. It is hardly probable that the presence 

 of a hypogynous cell is anything more than an adventitious resemblance 

 to 5. hypogyiia. In other essential points the two species are very dif- 

 ferent. In the latter the oogonia are borne in long chains or are inter- 

 calary and their walls are strongly pitted; the sporangia are of different 

 shape and proliferate abundantly internally, and the spores all swarm 

 at once. It is e\"ident that Achlya hypogyna is related to Achlya colorata 

 unQl A. racetnosa. The general habit, the structure of the oogonia, and 

 the sub-oogonial antheridia are very much the same as in A. colorata; 

 but the slender hyphae, the hypogynal cell, colorless oogonial walls, 

 and the smaller eggs easily distinguish the present species. 



-Maurizio suggests that sub-oogonial antheridia with hypogynous 

 tubes may be of generic value in Saprolegnia (1899), but such a suggestion 

 can scarcely be followed when we find this character present in only 

 one of a group of related forms, not to mention the variability of that 

 character in 5. hypogyna itself. 



In a \'ery few cases the oogonia are oblong and some intercalary 

 ones are occasionally seen. When the stalk is very short the anther- 

 idium ma>' extend some distance into the main hypha. Oogonia with 

 smooth walls are usually very few or none on ordinary media; occasionally, 

 however, a culture on insects in water may contain a good many such. 



Maurizio (F^lora 79: 149. 1894) and Kauffman (Ann. Bot. 22:382. 

 1908) think that the fertilizing tube in Saprolegnia hypogyna is not such, 

 "but represents a tendency to produce secondary growth, as in spor- 

 angia." It is important to note in this connection that there are two 

 kinds of growths into the oogonium. One kind is thin-walled and full 



