HOW TO KNOW THE FRESH-WATER ALGAE 



118b Cells some other shape; not living within animals 119 



119a Plant a much-branched, coenocytic tube (multi-nucleate and with- 

 out cross walls), growing in leaves of Araceae (Indian Turnip). 

 Fig. 92 PHYLLOSIPHON 



Fig. 92. Phyllosiphon Arisari 



Kuhn. a, portion of thallus 

 showing tangled threads; b, 

 habit of thallus in tissue of 

 host (redrawn from Just). 



This branched, tubular plant 

 is non-cellular; forms green 

 patches in the leaves of higher 

 plants which become discolored. It may be more widely distributed 

 than appears to be the case at present, but so far it is known only from 

 northern and eastern sections of the United States. 



Figure 92 



119b Plant not a branched coenocyte 



120 



120a An irregularly shaped, flask-like cell in the tissues of Ambrosia 

 (ragweed), and other plants. Fig. 93 RHODOCHYTR1UM 



Fig. 93. Rhodochytrium spilanthidis Lag. 



This curiously shaped, unicellular parasite oc- 

 curs on a greater variety of hosts than Phyllosi- 

 phon (Fig. 92), but seems to be most frequent in 

 ragweed. It is quickly identified by the red 

 color and the large number of strach grain that 

 Figure 93 are usually present. 



120b An irregularly oval, thick-walled cell in the tissues of Lemna 

 (duckweed). Fig. 94 CHLOROCHYTRIUM 



Fig. 94. Chlorochytrium Lemnae Cohn. a, 

 showing net-like chloroplast (redrawn 

 from Bristol-Roach); b, cell in host tisue. 



The duckweed, Lemna trisulca, is the 

 most common host for this endophytic 

 alga. Old plants of Lemna as they be- 

 come colorless in age, usually reveal min- 

 ute green spots caused by Chlorochytrium. 



There are probably three other species in 

 the United States, differentiated by cell size and thickness of the wall 

 which is usually much lamellated. 



Figure 94 



66 



