126 WISCONSIN PEYTOPLANETON 



Richteriella botryoides forma tetraedrica Lemmermann, Arch. f. Hydrobiol. 

 u. Planktonkde. 5: 307. 1910. 



Colonies of 4-8-16 or more cells in groups of four and disposed in a 

 quadrate or pyramidate manner with the groups of four in turn pyra- 

 midately or quadrateiy arranged. Cells spherical, with 1-5 long, hya- 

 line, delicately tapering setae on the face not adjacent to other cells. 

 Chloroplast single, parietal, cup-shaped; with one pyrenoid. (Eu- 

 planktont). 



Diam. cells (without setae) 3-7 /*; length of setae 20-35 /*,. 



Blake (rrr), Bone (sss), Chain (sss), Chetek (rr), East (IT), Green (1) 

 (rr), Hooker (rr), Horse (rr), Horseshoe (2) (rrr), Island (rrr), Little Bass 

 (2) (r), Little Crooked (rrr), Loveless (r), Mendota (rr), Monona (cc), North 

 Turtle (rr), Pokegama (3) (rr), Poor Farm (rr), Pope (rr), Prairie (rr), 

 Round (1) (rr), Tenderfoot (rrr), Tied Canoe (rr), Wolf (rrr). 



Flat sixteen-celled colonies with a central open space are the most 

 common. Such colonies have been given the form name fenestrata but 

 both it and the form tetraedrica are unworthy of recognition. On rare 

 occasions large colonies are found; colonies containing over 750 cells 

 having been collected from the plankton of Lake Monona. 



var. ELEGANS G. M. Smith. PI. 29, Fig. 1. 

 Trans. Wis. Acad. Sci., Arts, & Lett. 19 1 : 631, pi. 12, fig. 4. 1918. 



Cells with 5-7 setae on the exposed face. Dimensions as in the 

 typical form. (Euplanktont). 



Rice (1) (rr). 



This seems to be a distinct variety since the cells of colonies from 

 this lake all bore the large number of setae. 



MICRACTINIUM QUADRISETUM (Lemmermann) G. M. Smith. PI. 28, 



Fig. 4. 



Bull. Torr. Bot. Cl. 43: 479, pi. 25, fig. 17. 1916. 



Cells ovoid, with 1-4 long, delicately tapering setae on the exposed 

 faces. Chloroplast single, parietal, cup-shaped; with one pyrenoid. 

 (Euplanktont). 



Diam. cells (without setae) 4-7 ^, length 8-10 /x; length of setae 

 23-40 p. 



Bear Trap (rrr), Camp (rr), Cranberry (rrr), Eagle (rrr). 



The cells of this species are somewhat larger than those of M. pusH- 

 lum and are distinctly ovoid. The character upon which the specific 



