178 WISCONSIN PHYTOPLANKTON 



CHARACIUM GRACILIPES Lambert. PI. 49, Figs. 20-24. 

 Rhodora 11: 65, pi. 79, figs. 3-6, 9, 14-22. 1909. 



Cells straight or curved with the median portion fusiform; apex 

 tapering into a long seta and base attenuated to a filiform stipe. Chloro- 

 plast parietal, band-shaped, 1-32 per cell; with one pyrenoid in each 

 chloroplast. (Euplanktont). 



On Diaphanosoma brachyura. 



Cells 5-14 n broad, 70-480 /* long. 



Howey (cc). 



This alga was found on the same organism and at the same time as 

 C. cylindricum. It was confined to the forward appendages while 

 C. cylindricum was found at the tail only. 



Order ULOTRICHALES. 



Cells usually in a simple or branched thallus, rarely forming disci- 

 form thalli one cell in thickness. Thallus generally attached, rarely 

 free-floating; naked, or enclosed by a tough and leathery or copious 

 and gelatinous, homogeneous or lamellated envelope. Cells generally 

 with a single parietal laminate to cup-shaped chloroplast with one or 

 more pyrenoids. Cell shape usually cylindrical with flattened ends, 

 rarely cylindrical with rounded ends, spherical or cubical. 



Asexual reproduction by vegetative cell division, by a division of 

 vegetative or special cells to form 2-16 bi- or tetraciliate zoospores, and 

 by aplanospores. 



Sexual reproduction either isogarnous by a division of cell contents 

 to form bi- or tetraciliate zoogametes ; or heterogamous by the fusion of 

 tetraciliate zoogametes of different size or the union of large non-motile 

 oospheres and small biciliate antherozoids. 



KEY TO THE FAMILIES. 



Ctlls united to form simple filaments ULOTRICHACEAE 



Cells united to form branching filaments. 



Sexual reproduction by isogamous zoogametes CHAETOPHOBACEAE 



Sexual reproduction by heterogamous zoogametes APHANOCHAETACEAE 



Family ULOTRICHACEAE. 



Cells united to form simple free-floating or sessile filaments which 

 are enclosed at times by a copious, hyaline, homogeneous or radially 

 fibrillar, gelatinous envelope. Cell shape spherical to cylindrical with 

 rounded or flattened ends. Walls of cells delicate or thick, homogen- 



