142 
Blackman and Tansley. 
16. Chaetopeltis. Berthold, 1878. 
Thallus an epiphytic flat regular plate of a single layer of 
cells in close contact, usually with long filar processes 
growing out from the cell walls (sometimes absent) 
and irregularly distributed. The plate chloroplast is 
so thin in places that it simulates several separate 
discs. Quadri-flagellate zoospores and bi-flagellate 
gametes occur. 
17. Myxochaete. Bohlin, 1894. 
Thallus an epiphytic monostromatic plate of closely 
aggregated polygonal cells each with two filar pro¬ 
cesses growing from the free wall. Reproduction not 
observed. 
18. Nordstcdtia. Borzi, 1892. 
Thallus of clustered cells growing on bones. The cells 
hear filar processes which are very long and have a 
slightly thickened base. Imperfectly known. Chloro¬ 
plast described as star-shaped. 
it). Ulvella. Crouan, 1859. 
Thallus a well defined lenticular epiphytic plate v/ith 
several layers of round cells at centre and radiating 
long cells at the periphery. No setae or filar processes. 
Zoospores may arise from the centre cells. 
Fam. VI. Chaetosiphonaceze. 
Thallus an endophytic cylindrical or swollen branch-system, which 
is coenocytic in structure, being either entirely devoid of internal septa 
or having them only at rare intervals. Setae (in the strict sense) occur 
and the chloroplasts are discoid, when mature, by fragmentation of a 
parietal plate. 
Reproduction by quadri-flagellate zoospores. 
/ * ■ i i. . ' 1 
Genera. 
1. Chaetosiphon. Huber, 1892. 
Thallus endophytic in Zostcva- leaves, forming a 
straggling branch-system, which is constricted at 
irregular intervals, but only forms septa to delimit 
the zoosporangia. Erect setae (which may be 
secondarily occluded) project through the surface of 
the host. The chloroplasts are angular discs, free or 
united by fine processes. Nuclei large and moderately 
abundant, but sometimes only one occurs between 
two constrictions of the thallus. Zcopsorangium 
terminal and swollen, liberating the zoospores by a 
narrow tube which emerges through the surface of 
the host. 
