I 9 I 2] BARRETT— BLASTOCLADIA 355 



spread over the plate by rocking the same or by the use of a sterile 

 platinum loop. Thus distributed, the zoospores soor 



germinate 



produce large numbers of usually simple plants bearing the repro- 

 ductive organs. They commonly lie sufficiently close so that most 

 of the agar may be cut out and fixed for microscopic study. 



Three different killing solutions were used, which gave various 

 results. These were medium chrom-acetic acid, Flemmingr's weak 



alcohol 



fixer 



of 



from 



paraffin. Sec 



thick and stained 



The stains used were Flemming's triple stain with the orange G 

 dissolved in clove oil, Heidenhain's iron-alum hematoxylin, and 

 Gram's stain. The triple stain following Flemming's weak solu- 

 tion gave the best material for the study of the walls of the resting 

 sporangia, papillae of dehiscence, and for fragmentation of the 

 protoplasm to form zoospores; while Heidenhain's hematoxylin, 

 when preceded by medium chrom-acetic acid, gave much the best 

 material for the study of the protoplasm and nuclei. Gram's stain 

 proved very good as a nuclear stain. 



Description of the plant 



The plant consists of a basal cell or cylinder whose lower extrem- 

 ity is attached to the substratum by a system of rhizoids, and sup- 

 ports above a dichotomously Or umbellately branched system whose 

 final branchlets terminate in one or more reproductive bodies 

 (figs. 12, 58). At the points of origin of the branches, and occa- 

 sionally elsewhere, there are more or less well marked constrictions 

 of the mycelium. This character at once suggests a relationship to 

 the members of the Leptomitaceae. The constrictions, however, 

 are more abrupt and usually of less depth than those of that 

 family. They mark off the plant into definite segments which are 

 fairly constant in diameter throughout, although they occasionally 

 have a tendency to enlarge slightly at one or both ends. This is 

 especially 



which 



than two branchlets. In this 

 lets of Rhipidium americanun 



') 



