HOW TO KNOW THE FRESH-WATER ALGAE 



165b Chloroplast not axial, or more than 1 in a cell, without radiating 

 arms 167 



166a Chloroplast definitely star-shaped with a central pyrenoid; cells 

 spherical. See Fig. 51 ASTEROCOCCUS 



166b Chloroplast irregularly lobed, not symmetrically radiate, without 

 a pyrenoid; cells pyriform. Fig. 122 MYRMEC1A 



s- — -v Fig. 122. Myimecia aquatica G. M. Smith (re- 



J/^H^i^x >Q\ drawn from Smith). 



W r $^M%&) v^&'i These cells are either spherical or somewhat 



xsi ''-^W \£±j/ pear-shaped and usually show a thickening of 



the wall at one side, giving them an unsymmetri- 

 Figure 122 cal shape. Although the genus was originally 



described from aerial situations, specimens in 

 this country have been collected from aquatic habitats. 



167a (165) Cells spherical 168 



167b Cells oval or ellipsoid 174 



168a Cells large, wall thin; chloroplast irregular in shape and lumpy 

 with starch grains, arranged in radiating strands from the center 

 of the cell, and also parietal. Fig. 123 EREMOSPHAERA 



Fig. 123. Eremosphaera viridis De Bary. 



/Z&& w-.. "IT^v This is one of the largest spherical cells 



//r® '. <S\ (up to 800 microns in diameter) encountered 



II& ■» S-- - o°%. A\ amon< ? tne unicellular algae. Although usu- 



m 3^^|||p Q Jl a ^Y solitary it may appear in clusters within 



Q£»0 v^^fep^ °<d3/ t ^ ie °ld mother-cell wall. There is one other 



\\G £$■ W^k^ Jal rare species (with oblate-spheroidal cells) but 



X§><£>&& ''** *W/ the plant illustrated is fairly common in habi- 



^^T_ < ^°/y ta * s wnere desmids abound. The numerous 



^=^~2^^^^ disc-like chloroplasts are often lumpy and 



irregular in shape because of the starch 

 grains which collect about them. 



168b Cells not as above 



169 



81 



