arise from a conical protuberance, at the base of which are 2 con- 

 tractile vacuoles. Chloroplast cup-shaped, without a pyrenoid; pig- 

 ment-spot lateral and posterior. 



Spondylomorum quaternarium Ehrenberg 1849, p. 236 



PI. 3, Figs. 1, 2 



Cells narrowed and somewhat produced posteriorly to form blunt- 

 ly rounded points, 5-15fi in diameter. Colony 36-75/t in diameter. 



Reported by Stickney from a laboratory aquarium in Madison; to 

 be expected in the plankton of lakes rich in nitrogenous substances. 



Wis. 



FAMILY HAEMATOCOCCACEAE 



In this family the cells are peculiar in that the protoplast lies some 

 distance within the cell wall, to which it is connected by fine proto- 

 plasmic sh-ands. Between the wall and the protoplast there is a wide 

 layer of mucilage. There is a massive chloroplast, which in Sphae- 

 rella is usually masked by an abundance of haematochrome, a red 

 pigment which develops when the cell is dormant. There are 2 fla- 

 gella, several contractile vacuoles, and a lateral pigment-spot. 



Key to the Genera 



Cells solitary Haematococcus 



Cells in colonies, forming a circumferential band in a 



spheroidal gelatinous investment Stephanosphaera 



Haematococcus C. A. Agardh 1828, Icon. Algar., PI. 22. 



Cells ovoid to ellipsoid, having 2 widely diverging flagella from an 

 anterior papilla; protoplast separated from the wall by a wide en- 

 velope of mucilage through which cytoplasmic sti^ands radiate; 

 pigment-spot lateral. Cells frequently appearing in a stationary 

 ( akinete ) condition in which haematochrome pigment becomes pre- 

 dominant (assumed to be an adjustment to intense illumination, 

 especially when the water is shallow). At least 1 species of the genus 

 has been reported from red snow of alpine and subalpine regions. 



Haematococcus lociistris ( Girod. ) Rostafinski, 1875, p. 139 

 Sphaerella lacustris (Girod.) Wittr. 

 PI. 2, Fig. 2; PI. 3, Figs. 3-5 

 Cells ellipsoid or ovoid; chloroplast apparently cup-shaped, some- 

 times appearing axial and usually masked by haematochrome; cells 

 variable in diameter, 10-50/a in the encysted condition. 



[80] 



