WISCONSIN PHYTOPLANETON 99 



eal chloroplast, one eyespot, and a pair of contractile vacuoles at the 

 base of the two cilia. 4-14 asexual reproductive cells giving rise to 

 autocolonies. Colonies generally dioecious, with 3-9 oospheres and 

 about half of the cells developing into antherids that contain 16-32 

 fusiform antherozoids with two terminal cilia. Zygote smooth-walled. 

 (Facultative Planktont). 

 Cells 5-9 /A in diam. ; colonies 200-680 /*, in diam. 



Beaverdam (rrr), Camp (sss), Center (ss), Delavan (ss), Eagle (rr), Eliza- 

 beth (rrr), Fowler (rrr), Jennie (rrr), Kawaguesaga (rrr), Lac du Flam- 

 beau (rr), Lac la Belle (rr), Mill (rrr), Oconomowoc (rrr), Paddock (r), 

 Pokegama (1) (rr), St. Croix (rrr), Silver (2) (rr). 



Volvox mononae sp. nov. PI. 18, Fig. 1. 



Colonies spherical, containing a comparatively small (400-2500) 

 number of cells. Cells spherical, not connected with one another by 

 cytoplasmic processes. Individual sheaths of cells confluent with colon- 

 ial envelope. Cells containing a single bell-shaped chloroplast with 

 one pyrenoid, an eye spot, and two cilia whose length is 2-3 times the 

 diameter of the cell. 3-10 asexual colonies formed inside the coeno- 

 bium and these daughter colonies in turn frequently containing young 

 colonies. Asexual reproductive cells becoming much larger than vege- 

 tative cells before division commences. Colonies dioecious, with oogonia 

 and antheridia in young daughter colonies only. 20-60 cells of a 

 young colony formng typical Volvox antheridia that generally contain 

 64 antherozoids. Female colonies with 6-10 oospheres. Zygote smooth 

 walled. 



Vegetative cells 5-8 /x in diam. Colonies 50-350 //, in diam. 



Monona (aaa). 



Order PROTOCOCCALES. 



Vegetative cells immobile ; free-floating, sessile, or epiphytic ; solitary 

 or in colonies. Colonies amorphous and frequently embedded in a 

 gelatinous envelope; or of definite shape and with or without a gelati- 

 envelope. Colonies capable or incapable of increasing the number of 

 their cells after they are formed. Cells variously shaped, generally 

 with one chloroplast and pyrenoid. 



Asexual reproduction by zoospores, fragmentation of the colony, auto- 

 spores, or autocolonies. Resting akinetes known in some species. 



Sexual reproduction by isogamous zoogametes known but not found 

 in a majority of the genera. 



