38 AQUATIC PHYCOMYCETES 



ingly difficult forms to propagate. Thraustochytrium proliferum, a ma- 

 rine species saprophytic on Bryopsis, has recently been secured in 

 pure culture by Reischer and Watson (in Vishniac, 1955b). 



Of the Peronosporales considered, Cantino (1949b) has repeated 

 the success, previously achieved by Ito and Nagai (1931) and Drechsler 

 (1932), of raising Pythiogeton in pure culture. He also made a study of 

 its physiology. Recently, Prowse (1954b) reported the rotifer-capturing 

 Zoophagus insidians in pure culture for the first time. 



Preservation 



The most useful method in preserving aquatic Phycomycetes so as 

 to make them readily available for examination is by the preparation 

 of permanent mounts. Water mounts of material are mordanted with 

 a weak solution of acetic acid; they are then washed and eosin in 10 

 per cent glycerin solution is run under the cover glass. After the so- 

 lution has concentrated to pure glycerin and eosin, the slide is sealed 

 with a cement. Instead of glycerin and eosin, Amann's (lactophenol) 

 mounting medium, to which either acid fuchsin or cotton blue has been 

 added, makes an excellent preservative. When tightly sealed such prep- 

 arations last for many years. In dealing with minute forms such as 

 chytrids on algae, in which the material may frequently be very scanty, 

 either the infected substratum may be isolated on another slide and 

 preserved or the whole lot of material may be preserved on the slide 

 and the region where the infected filament lies encircled with India ink. 



A. F. Bartsch, of the University of Wisconsin, has kindly outlined, 

 in a personal communication, a method he has used with excellent re- 

 sults on material of Blyttiomyces spimdosus, a parasite of the zygospores 

 of Spirogyra. His procedure may be summarized as follows: The mate- 

 rial is fixed in a small vial in formalin-acetic acid alcohol (glacial acetic 

 acid, 5 cc. ; commercial formalin, 5 cc. ; 50 per cent ethyl alcohol, 90 cc.) 

 for three days. It is then washed by adding small amounts of water to 

 the vial, shaking slightly, and pouring off the fluid. This is continued 

 until the odor of the acetic acid is gone. The water is now poured off 

 again and a solution of 0.5 percent iron alum is added. After twelve 

 hours the iron alum is washed out with three changes of water. About 

 seven drops of 1 per cent haematoxylin in 95 per cent alcohol is then 



