2 39 
Classification of Green Alger. 
Series III. Vaucheriales. 
Plant-body always coenocytic. Chromatophores numerous, 
parietal, discoid, yellowish and devoid of pyrenoids ; starch or oil 
may be the reserve material. Asexual reproduction by zoospores, 
aplanospores or akinetes. The simple swarmers possess two flagella 
of about equal length, one directed forwards and the other backwards. 
Fam. I. Vaucheriaceae. 
Plant-body a branched tubular thallus, aquatic or terrestrial, and 
usually with‘root’ branches. Asexual reproduction by ‘synzoospores ’ 
aplanospores or akinetes. Sexual reproduction by oogamy; the 
oogonia arising by swelling of the ends of branches of the thallus, and 
containing a single egg-cell rich in chlorophyll, the antheridia arising 
similarly and containing numerous colourless antherozoids, with two 
opposed flagella, attached a little way from the apex ol the antherozoid. 
Reproductive regions always delimited by septa. 
Genera. 
i. Vaucheria. De Candolle, 1803 . 
The thallus never branches truly dichotomously. Oil 
is the assimilatory reserve product. Asexual repro¬ 
duction by oval compound zoospores, containing a 
number of nuclei, and covered superficially with 
pairs of flagella, one pair to each nucleus. 
Dichotomosiphon. Ernst, 1902 . 
The thallus branches dichotomously. Starch is the 
assimilatory reserve product. Asexual reproduction 
by swollen segments of the thallus (akinetes) which, 
after resting, give rise to new branches. No zoospores 
observed. 
Fam. II. Phyllosiphonaceae. 
Plant-body endophytic and more or less parasitic. Reproduction 
only by the formation of numerous aplanospores , which are expelled 
by swelling of the inner layer of the thallus wall. No septa formed to 
limit the reproductive region. No sexual reproduction. 
1 . Phyllosiphon. Just, 1882 . 
Thallus a much-branched tube parasitic in leaves. 
Both oil and starch grains occur. 
2 . Phytophysa. Weber van Bosse, 1890 . 
Thallus globular, parasitic in the cortex of stems of 
higher plants. Oil and cellulose (?) grains occur. In 
reproduction, the peripheral protoplasm forms aplano¬ 
spores, while the central part forms a cellulose 
“ kernel,” between which and the swelling thallus wal 
the spores become squeezed, and are finally expelled 
by rupture of the wall. 
Note.— It was originally our intention to include in this revision, 
the Glaucophyceae (cf. Introduction p. 19), but further consideration of 
