Classification of Green Algce. 143 
2. Blastofhysa. Reinke, 1888. 
Thallus endophytic, consisting of a chain of large 
globular vesicles which may be separated by short 
tubes, or may arise in close contact with one another 
by ‘ budding.' The connecting tubes at first contain 
protoplasm and chloroplasts, but the contents are 
afterwards withdrawn into the vesicles, and these 
become occluded by septa from the empty tubes and 
from one another. In slide-cultures the tubular 
thallus predominates. Chloroplasts are angular discs, 
formed by fragmentation and lining the vesicle wall. 
Setae occur projecting from the host, sometimes in 
great numbers. The contents of a vesicle may divide 
into a large number of zoospores, which escape 
through a narrow projecting tube. 
[In constitution, these two genera recall the Siphonales, to which 
(especially to Vnlonia) they have been related by most authorities. 
They have, however, so many points (endophytic habit, exactly com¬ 
parable setae, fragmenting plate-chloroplast, sporangial emission-tube, 
and quadri-flagellate zoospores) in common with certain genera of the 
fourth section of the Chaetophoraceae that this seems rather to be their 
true affinity, and we must consider that their siphoneous thallus is a 
secondary evolution quite apart from the phylum of the Siphonales. 
The fact that slide-cultures of Blastophysa are but slightly vesicular 
seems to indicate that the tubular thallus is primitive and the Valonia -like 
swellings only secondary.] 
Fam. VIT. Chaetosphaeridiace^e. 
Thallus epiphytic consisting of a reduced clustered branch-system 
invested with dense or thin mucilage. Cells globular with a single 
parietal chloroplast and one pyrenoid. All or some of the cells bear 
each an erect sheathed seta ov sheathed filar processes. Reproduction not 
observed, but zoospores undoubtedly occur. 
[The three genera now united in this family have been assigned very 
various systematic positions by the few writers who have worked on them. 
The view here taken is to regard them as combining the epiphytic 
reduced branch-system characteristic of the Chaetophoraceae with the 
truly sheathed setae of the Coleochaetaceae. The accounls of the 
structure of the setae are not always harmonious. Probably the* sheath’ 
is in all cases at first an outgrowth of the cell-cavity, then its cuticle 
becomes ruptured at the apex and the inner layers grow on with a reduced 
diameter as a seta with a distinct lumen ( Coleochaete ), or with an extremely 
fine lumen ( Chaetosphaeridium) or as a filar process quite devoid of 
lumen (Cunochactc).'] 
Genera. 
1. Chaetosphaeridium. Klebahn, 1892. 
Thallus epiphytic, consisting when mature of rounded 
green cells, united by longer or shorter empty tubes 
(sometimes hardly detectable) to form a sort of 
sympodial branch-system. Each green cell is capable 
ol dividing to form two hemispherical cells of which 
the upper only puts out an erect sheathed seta, while 
the lower grows out laterally into a tube, the contents 
of which become aggregated at the growing end and 
are cut off to form a new green cell. Chloroplast a 
