SOME NOVA SCOT1AN AQUATIC FUNGI. MOORE. 219 



The sexual reproduction in the order is by means of 

 oogonia and antheridia. The former are, as a rule, spherical 

 and terminal on the main filaments or lateral branches, or at 

 times intercalary, when they may be spherical, barrel shaped or 

 cylindrical. The antheridia are cylindrical, club shaped or ovate 

 cells cut off i'rom the ends of special branches which become 

 appressed against the walls of the oogonia, and in some cases at 

 least send through the walls of the latter organs fertilisation 

 tubes. A modification of the common type of antheridium is 

 found in Saprolegnia hypogyna Pringsheim, and in Achlya 

 hypogyna Coker & Pemberton 1 . In these species an antheridial 

 cell is cut off from the oogonial branch by a septum a short 

 distance below the basal wall of the oogonium. and a tube-like 

 growth from this basal wall pushes up directly into the cavity 

 of the latter organ. In some forms antheridia are absent, and 

 it appears to be doubtful whether in the great majority of the 

 first two families of the group, even when they are present, 

 they have not become functionless. The contents of an oogonium 

 gives rise to one or more oospheres which ripen into resting 

 oospores and lie free in the cavity of the oogonium. The ripen- 

 ing process generally occupies two or more weeks. In the ripe 

 condition the fat contents of an oospore usually collect in one or 

 a few large globules. When the oil globule occupies one side of 

 the spore and is not included by the remaining spore contents, 

 the spore is described as " excentric." When the oil globule is 

 surrounded by the other spore contents the descriptive term 

 " centric " is applied. A good example of the first is found in 

 Achlya americana Humph., an 1 of the second condition in 

 Achlya apiculata DeBary. 



The walls of the oogonia may be smooth or provided with 

 more or less numerous outgrowths ; they may become uniformly 

 thickened or definite areas may remain unmodified, giving rise 

 to pits. These unthickened areas or pits are best brought out 

 by treatment with chlor-zinc-iodine solution, which gives to the 



