On tufts of bristles in Pediastrum and 

 Scenedesmus. 



By 



Johs. Boye Petersen. 



In the autumn 1909 I made a continued plankton investi- 

 gation of some ponds near to the villages Bistrup and Stavns- 

 holt to the north of the lake Fure Sø (North Sealand). During 

 this investigation I used among others the cilia staining method 

 indicated by Löffler in order to examine the cilia of some Chla- 

 mydomonadaceœ. In my preparations there also occurred several 

 specimens of Scenedesmus quadricauda, acuminatus and acutus, and 

 I observed some very fine threads or bristles projecting, either 

 from the points of the cells, or, seemingly without any order, from 

 the surface of the coenobia. I then fancied to examine into this 

 more carefully, and continued investigations showed me similar 

 bristles in all the following species: 



1. Scenedesmus quadricauda (Turp.) Bréb. 



a. typicus Kirchn. Fig. 3. 



b. abundans Kirchn. Fig. 4. 

 (and perhaps in other varieties). 



2. Scenedesmus Opoliensis Richter. 



3. Scenedesmus acutus Meyen. Fig. 5. 



4. Scenedesmus acuminatus (Lagh.) Ghod. Fig. 6. 



5. Scenedesmus denticulatus Lagh. 



6. Pediastrum simplex Meyen var. clathratum. Fig. 2, 7, 8. 



7. Pediastrum duplex Meyen. 

 a. genuinum (A. Br.). 



ß. clathratum (A. Br.). Fig. 1, 9—11. 

 y. reticulatum (Lagh.). 



8. Pediastrum Boryanum (Turp.) Menegh. Fig. 12. 



Botanisk Tidsskrift. 31. Bind. 



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