166 
Blackman and Tansley. 
q. Dcrmatopliyton. Peter, 1886. 
Thallus irregularly discoid, growing in fissures in the 
shell of a fresh water tortoise. The central part of the 
disc becomes many-layered by secondary divisions. 
Zoosporangia peripheral, flask-shaped, producing 
many zoospores. 
[The true systematic position of this alga is uncertain. Schmidle 
has found it to be multinucleate and proposes to unite it, on morphological 
grounds, with Ulvclla (in the type-species of which, however, the number 
of nuclei in the cell is still unknown) assigning both forms to the 
Cladoplioraceae] 
Sub-Family II. 
Chroolepideae. Aerial forms; haematochrom abundant in the 
vegetative cells. 
Genera. 
'"Thallus freely branched, partly creeping and partly erect. 
10. Trentepohlia. Martins, 1817. 
Thallus an irregular or dichotomous branch-system of 
very varied habit. Cells usually short with several 
angular chloroplasts and no pyrenoids. Reproduction 
by biflagellate zoospores or isogametes which arise in 
large numbers in swollen terminal thallus-cells, 
often of very specialised form. 
'"'"Thallus epiphyllous, a pseudo-parenchymatous disc produced by 
the concrescence of a branch system and with only short erect 
branches. 
11. Pliycopeltis. Millardet, 1870. 
Thallus a rounded disc epiphyllous on aerial evergreen 
leaves, and devoid of rhizoid-branches. Chloroplasts 
several in the cell and without pyrenoids. Repro¬ 
duction by biflagellate zoospores, devoid of eye-spot, 
arising in large numbers in the zoosporangia. 
12. Cephaleuros. Kunze, 1828. 
Thallus a lobed disc of one layer of cells bearing much- 
branched unicellular rhizoids below, and sometimes 
also tapering erect branches. The thallus spreads 
below the cuticle of thick leaves and is partly parasitic. 
Chloroplasts small, discoid, several in the cell and 
without pyrenoids. 
Zoosporangia large, swollen, terminal, producing a 
number of bi-flagellate zoospores. 
Class II.—STEPHANOKONTAE. 
Motile reproductive cells with a crown of cilia round the clear 
anterior end. 
[The only known forms of this class are filamentous.] 
