WISCONSIN PHYTOPLANKTON 177 



CHAKACIUM CYLJNDRICUM Lambert. PI. 49, Figs. 16-19. 

 Rhodora 11: 70, pi. 79, figs. 1-2, 7-8, 10-13, 23-25. 1909. 



Cells cylindrical, with, rounded apices, base tapering slightly into a 

 short stipe without a basal disc. Chloroplasts 1-16, parietal, disciform 

 to laminate, without pyrenoids. (Euplanktont). 



On DiapJianosoma brachyura and Branchipus vernalis. 



Cells 8-20 n broad, 20-430 p. long. 



Howey (cc). 



The lack of a pyrenoid suggests Characiopsis but the bright green 

 color of the chloroplast shows that the alga is one of the Chlorophyceae 

 and so is placed among Characium species. Young cells contain a sin- 

 gle chloroplast but with growth there is an increase in the number of 

 chloroplasts and all stages between cells with a single chloroplast and 

 those with sixteen may be found on the same crustacean. Lambert 

 holds that this condition is a stage in the division into zoospores but 

 in my opinion it is the normal condition of the adult cell. Another 

 point of interest is the position of the alga upon the host since it is 

 only found on the tail of the crustacean. 



CHARACIUM LIMNETICUM Lemmermann. PL 49, Figs. 25-29. 

 Bot. Not. 1903: 81, pi. 3, figs. 7-10. 1903. 



Cells broadly fusiform, lunate, rarely straight; apex produced into 

 a single delicate hyaline seta; base a delicate stipe without basal discs. 

 1-8 parietal band-shaped chloroplasts, each containing 1-2 pyrenoids. 

 (Euplanktont). 



Cells 5-14 /* broad, 25-110 /* long; stipe 5-10 p long. 



On Diaphanosoma brachyura. 



Boulder (rr), Browns (rr), Delavan (rrr). 



Lemmermann describes the chloroplast as single but reports a divi- 

 sion of the chloroplast prior to division. I have found that in all nor- 

 mal adult cells of C. limneticum, C. gracilipes, and C. cylindricum there 

 is more than one chloroplast. 



The species is very closely related to C. gracilipes but is much 

 smaller, proportionally broader, and has a simple stipe. It is very 

 probable that Raphidium longissimum var. septatum Chodat (Ankistro- 

 desmus longissimum var. septatum (Chodat) Brunnthaler) is a cell of 

 C. limneticum broken off from the crustacean during collection. 



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