134 
Blackman and Tans ley. 
7. Micvodictyon. Decaisne, 1839. 
Thallus a thin sheet of indefinite outline attached by 
rhizoids at its centre and composed of septate branches, 
all in one plane and united by tenacula to form an 
irregular network. Cells all of similar size. 
8. lioodlea. Murray & De Toni, [889. 
Thallus a spongy mass of septate filaments branching 
irregularly in all directions and united together by 
tenacula. 
9. Cystodictyon. Gray, 1866. 
Thallus resembles that of Micvodictyon , but differs in 
that the branch system is differentiated into long and 
short cells. 
10. Anadyomene. Lamouroux, 1812. 
Thallus irregularly frondose and attached by a very short 
stalk; composed of a system of septate branches 
with long and short segments united in a plane 
without any interspaces and often hotbed on both 
faces with an additional layer of isodiametric branch- 
segments united to form a pseudo epidermis. Zoospores 
observed. 
”i ; Tha 11 us secondarily septate, ol many segments, but not developing 
as a branch system. 
11. Dictyosphaevia. Decaisne, 1842. 
Thallus when adult a very irregular basin-shaped or flat 
layer of large hexagonal cells closely united by 
tenaculum-cells. Secondary series of small cells may 
occur along the lines of juncture of the hexagonal 
cells. The thallus arises by the successive subdivi¬ 
sion of the protoplasmic contents of an embryonal 
globular ccenocyte to form a solid mass of compressed 
cells, which, by growth, becomes hollow and then 
bursts. 
Fam. VIII. Gomontiace^e. 
Thallus a minute , radiating , septate, branch-system. Reproduction 
by zoospores and by swollen aplanosporangia, which may\be detached 
and live for a time independently. Marine. 
Genus. 
1. Gomontia. Bornet and Flahault, 1888. 
Thallus dorsiventral, growing in the substance of shells 
and sending down perforating rhizoids. “Cells’’contain 
