HOW TO KNOW THE FRESH-WATER ALGAE 



197b Cells a little longer than wide, rectangular, with a narrow median 

 incision; 4-lobed in end view; poles of young cells infolded. Fig. 

 139 PHYMATODOCIS 



Fig. 139. Phymatodocis Nordstedti- 

 ana Wolle. 



Although rarely found this fila- 

 mentous desmid may be the domi- 

 nant form in some habitats that are 

 especially favorable. The cells ap- 

 Figure 139 pear somewhat quadrangular when 



seen in front view (as they occur 

 in the filament) but are quadrilaterally symmetrical and are 4-lobed 

 as seen in end view. 



198a (190) Chloroplast parietal, of various shapes, 

 net-like, ring-like, or plate-like, with pads and 

 thin areas (Fig. 139 l A): or ii axial, plants in 

 the form of a macroscopic thallus as in Fig. 

 153 210 



Figure 139'/4 



198b Chloroplast axial, a broad band, or star- 

 shaped; if parietal, in the form of a ribbon 

 as in Fig. 139 1 /2,* microscopic 199 



gg l^^l^^ j 



f O 



Figurr 139% 



(The following genera are determined with difficulty when in the 

 vegetative condition alone; reproductive structures and 'fruiting' stages 

 are often necessary for completely satisfactory identification.) 



199a Chloroplast 1 or 2 in a cell; stellate, with radiating processes from 

 a central core which includes a pyrenoid 200 



199b Chloroplasts other shapes. 



203 



91 



