A ae, ی‎ LL 
ULOTHRIX 145 
present, excepted) capable of division and of transformation into 
sporangia. Each cell contains one band-shaped or reticular, or 
one to several disk-shaped chromatophores. Vegetative repro- 
duction by breaking apart of the cells to form new filaments. 
Asexual reproduction by means of zoöspores which germinate im- 
mediately or after a period of rest, by akinetes, and by aplanos- 
pores. Sexual reproduction through isogamous fertilization or 
conjugation of gametes of similar size and character. 
Synopsis of Genera 
Filaments E chromatophore a homogeneous, zonate band, with one to several 
pyrenoi I. ULOTHRIX 
Filaments not 28 chromatophore a parietal disk or plate, vg one pyrenoid. 
. STICHOCOCCUS. 
Filaments generally not attached; chromatophore granular, =o more or less com- 
pletely the whole cell wall, containing starch but no pyreno 
IIT. MICROSPORA. 
Filaments attached only when young; chromataphores several, کک"‎ without 
- TRIBONEMA. 
With the exception of Ulothrix and Stichococcus the genera of 
this family are not closely related. These two may be considered 
as having a common origin from a unicellular form, or the former 
may be derived from the latter. AZcrospora, in its chromatophore 
structure at least, shows some affinity with A/zsoclonium of the 
Cladophoraceae, although it is always distinguished from the latter 
by the absence of pyrenoids, and the single nucleus. 
Tribonema in all probability had a different origin and is appar- 
ently more closely related to the Ophiocytiaceae than to the other 
genera of the Ulothricaceae. 
I. ULOTHRIX Kützing, Flora, 16: 517-521. 1833 
Hormiscia Aresch. Act. Reg. Soc. Sci. Upsal. III. 6': No 
2. p. 12. ۸. p. 1866. Not Fries, Flor. Scan. 327. 1835. 
Including Hormospora Bréb. Ann. Sci. Nat. Bot. III. r: 25. 
1844. (?) 
Filaments consisting of a single series of uninucleate cells, all 
(except the rhizoid-like basal cell) capable of division and repro- 
duction. Chromatophore a homogeneous parietal band (some- 
