I 20 
Blackman and Tansley. 
Reproduction by typical zoospores observed in several cases. 
Gametes not known. All the forms are strictly marine. 
Genera. 
^Thallus strictly siphoneous. 
t. Halicystts. Areschong, 1850. 
Thallus entirely unseptate, globoid, and attached by a 
delicate stalk and disc. No rhizoid system. Chloro- 
plasts blunter-angled than in Valonia. Described as 
containing no starch. 
[Schmitz has suggested the removal of this genus into the true 
Siphoneae, and Apjchnia should perhaps go with it. The absence of 
starch and rhizoids make its position doubtful until the development is 
fully known.] 
2. Apjchnia. Harvey, 1855. 
Thallus erect, cylindrical, repeatedly polytomously 
branched, with constrictions at the points of origin of 
the branches, attached by a branched rhizoid system. 
The whole thallus is devoid of internal septa. 
**Thallus a secondarily septate branch-system, without septa at the 
points of origin of the lateral branches. 
3. Siphonocladus. Schmitz, 1878. 
Thallus either erect, columnar and slightly branched, or 
of confervoid habit, filamentous, and abundantly 
branched. The septa do not appear until the thallus 
has developed to a considerable size. Zoospores 
observed. 
4. Chamaedoris. Montagne, 1842. 
Thallus consisting of a stout unseptate cylindrical stalk 
bearing above a large cup-like head composed of 
numerous filamentous irregular branches tightly inter¬ 
woven. 
***Th a llus a secondarily septate branch system, septa always 
occurring at the points of attachment of the lateral branches. 
5. Valonia. Ginnani, 1757. 
Thallus typically branched. The septa appear late in 
development and cut off lenticular, multinucleate, peri¬ 
pheral portions of the protoplasm, which may grow 
out into shoot or rhizoid branches of the thallus. 
Some species are globular and unbranched and possess 
only the single septum which always cuts off the uni¬ 
locular rhizoid system from the shoot. Zoospores and 
aplanospores (?) observed. 
(To he continued.) 
II. Mudley, Printer, Whitfield Street, W. 
