7 2 The Botanical Gazette. [March, 



zoospore. In some cases, too, they have not acted with suffi- 

 cient promptness to fix the spore at precisely the right in- 

 stant. In view of these facts attempts have been made to 

 find a more satisfactory method 'of treatment, and I have 

 adopted after numerous trials a combination somewhat differ- 

 ent from any which I have seen suggested, though it involves 

 nothing new in principle. 



The zoospores, in water under a supported cover-glass, are 

 instantly killed by placing at the edge of the cover a couple 

 of drops of a one per cent, solution of osmic acid. This is 

 left for a few minutes to fix the spores thoroughly, which it 

 does without the least distortion, and is then drawn off by 

 means of filter-paper. It is not necessary to wholly remove 

 the acid or to pass water under the cover before applying the 

 staining fluid, which consists of a drop of a moderately strong 

 solution in 90 per cent, alcohol of Hanstein's rosanilin-violet, 

 composed of equal parts of fuchsin and methyl-violet. " This 

 stains the cilia and the bodies of the zoospores of both Algae 

 and Fungi very quickly and deeply, as well as sharply, show- 

 ing the number and insertion of the cilia as plainlv as a draw- 

 ing, and giving a clear image with the camera lucida. 



It is very possible that other stains would serve equally 



well, but I have not taken time nor has it seemed worth while 



to seek further in view of the uniformly good results obtained 



' as described. For killing and fixing, I think there is nothing 



quite so good in all respects as osmic acid. 



By means of the above treatment I have had no difficulty 

 in demonstrating the correctness of the statements of Cornu 1 

 and Hartog 2 that the zoospores of Achlya are ciliate, at least 

 in some cases, when they escape from the /.oosporangium, as 

 are those of Saprolegnia. This statement is directly opposed 

 to those of other writers and to those of the leading text- 

 books. - ? winch state that the zoospores of Achlya escape from 

 the sporangium without cilia. My observations were mad. 

 on a form related closely to A. polyaudra (perhaps that spe- 

 cies) and seem to me entirely conclusive. The discussion of 

 the details of the structure of the zoospores and of the bear- 

 ings of the fact stated is reserved for a future occasion; but it 



'Ana. Sci. Nat. ser. .">, torn, xv, p. 1. 

 ; Quart Jotirn Mic. Sci. vol. xxvii, p. 4-27 



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