CHAPTER X 
PHYLUM IV. SIPHONOPHYCEAE 
THE TUBE ALGAE 
264. These plants are filamentous, saccate or erect- 
dendroid, and are composed of coenocytes instead of dis- 
tinct cells. In the first (primitive) forms the plant body 
consists of a row of long bi- or poly-nucleated segments 
(coenocytes) arranged in a simple or branched filament, 
which is more commonly rooted below. When the fila- 
ment has cross partitions it is said to be septated. In 
many Tube Algae there are no partitions in the vegeta- 
tive portions of the plant, and such are said to be 
continuous. 
265. They are propagated (1) by the internal division 
of the protoplasm of a coenocyte (sporangium), or even of 
the whole plant into spores (ciliated zoospores in the 
water—walled spores in the air) ; (2) by the condensation 
of definite masses of protoplasm directly into thick-walled 
spores (chlamydospores). Their generation shows all 
gradations including the union of (1) ciliated isogametes; 
(2) ciliated heterogametes; (3) ciliated sperms, with eggs; 
(4) antherid nuclei, with eggs—in all cases producing 
zygotes, which usually become thick-walled resting 
spores. 
266. The dominant idea here is the development of 
coenocytes instead of distinct cells, and this has been 
consistently adhered to even when the plant body has 
shown otherwise a considerable amount of differentiation. 
184 
