36 THE SAPROLEGXIACEAE 



In the Wilmington plant, that we will call Form B, the oogonia and 

 the number of eggs run distinctly larger, all other characters the same. 

 For example, tw^o cultures of each were compared, one of each on a piece 

 of corn grain, and one of each on a mushroom grub. On the corn the 

 Chapel Hill plant showed oogonia 33-8 i|x; eggs 1-8, mostly 2-6, many 

 single; while Form B showed oogonia 65-9351, eggs 4-20, mostly 8-12 

 in an oogonium. On a grub the former showed oogonia 40-641X, eggs 

 1-5, mostly 2-4, while Form B showed oogonia 48-70[j., eggs 2-8, mostly 

 4-6. In Form B the first cultures which were made in the ditch water 

 with algae, etc., in which it was taken, showed a remarkable abnor- 

 mality (pi 10, figs. 5 and 6). A good many of the oogonia were much 

 swollen to as much as twice the average size (up to I50ja), while the eggs, 

 which were no greater in number than usual, were in great part disorgan- 

 ized, often only one or two maturing. The disorganized eggs would 

 usually reach the point of forming a thin wall, and would then go to 

 pieces inside. This condition was not thoroughly realized until after the 

 culture had been purified on agar and the abnormality thus arrested. 

 It was then found from slides that the enlarged oogonia contained a 

 parasitic organism with the exact appearance of a blue-green alga, which 

 ran among the eggs. There was not the least resemblance to the ordinary 

 fungal parasites that attack the water molds, and it is to be regretted 

 that the parasite was lost before it could be more thoroughly studied. 

 It is of interest to note the close resemblance of this parasite to the one 

 shown by Reinsch ('78) in his fig. 11, pi. 14. He considered the parasite 

 a species of Saprolegnia, but gives no reason for thinking so. 



The following observations were made on the Wilmington Form B 

 by Mr. J. N. Couch, Instructor in Botany: "The oogonial wall is thick- 

 ened just before the protoplasm draws away to form the egg initials 

 and as the eggs become rounded the fertilizing tubes appear. They grow 

 rapidly and in fifteen minutes have reached the eggs. Granules were 

 observed to pass slowly down the tubes and some of them seemed to dis- 

 appear into the eggs." The notes given below all refer to the Chapel 

 Hill form. 



Repeated cultures in spring water show that growth through old 

 sporangia is much more common in spring water than in distilled water, 

 where there is a strong tendency to proliferate as in Achlya. 



On emergence the large spores are elongated and often bent, squar- 

 ish at one end. They change this shape to pear-shape in a few seconds. 

 The ciliated end usually, if not always, emerges last. The opposite 

 end is often indented on emergence. Both large and small spores ap- 

 peared in large numbers in a hanging drop of sporangia and gemmae 

 in pure water. The spores are certainly diplanetic: some sporangia were 



