. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . f his extensive West Indian investigations, discriminatesbetween four sub-families of the Valoniaceae. Sub-family In this, the most primitive division of theValoniacese, the thallus consists at first, and in Valonia ventricosa always, ofa single large sac-like coenocyte which typically becomes branched. Septasoon appear, cutting off small lenticular, multinucleate, peripheral portions ofthe protoplasm (fig. 162 a, a). In Valonia th
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . f his extensive West Indian investigations, discriminatesbetween four sub-families of the Valoniaceae. Sub-family In this, the most primitive division of theValoniacese, the thallus consists at first, and in Valonia ventricosa always, ofa single large sac-like coenocyte which typically becomes branched. Septasoon appear, cutting off small lenticular, multinucleate, peripheral portions ofthe protoplasm (fig. 162 a, a). In Valonia these lenticular segments mayremain small or they may grow out and form segments as large as the parent- 252 Siphonodadiales segment from which they were derived (fig. 162 A). Successive formation ofbranch-segments sometimes results in a thallus with dichotomous or verticillatebranches, although as a rule the branching is irregular. The main coenocyteis attached to its substratum by numerous well-developed rhizoids or haptera(fig. 162 G), which grow out from the small lentiform segments that occurin great numbers at the basal end of the adult Fig. 162. Valonia utricularis (Both.) Ag. A, complete plant showing a stem-cell with fivebranch-cells grown out from the apex and two rim-cells (a, a) which have not yet grownout into branch-cells ; near the base of the stem-cell are numerous smaller rim-cells and three at the extreme base have grown into rivet-shaped rhizoids, x 4. B, singlecosnocyte developing zoogonidia. C, older rhizoids. D, zoogonidia. E and F, developingzoogonidia. (A, after Schmitz ; B—E, after Famintzin, from Wille.) In Dictyosphseria the contents of the very young coenocyte, which may beovoid, cylindrical or irregular, are divided by segregative cell-division, firstinto several coenocytes, and afterwards by successive segregative divisionsinto numerous segments which are so compact as to be angular by compres-sion. Numerous small lenticular cells (th
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