. Botany of the living plant. Botany. GREEN ALGAE 3^5 out (p. 140) how, as a set off against it, the more compUcated forms of the Siphoneac have acquired additional meclianical strenijth, either by internal cellulose ties, as in Caulerpa {Y\g. 333), or by matting' of their branches together, as in Codium, or by cementing tho*«c branches together, as in Halimeda. But these are concessions to an essentially weak construction. It is only possible to carry it to any considerable size when hving in water, and all the larger forms are marine. Vanchevia is an exception : for though many of its specie
. Botany of the living plant. Botany. GREEN ALGAE 3^5 out (p. 140) how, as a set off against it, the more compUcated forms of the Siphoneac have acquired additional meclianical strenijth, either by internal cellulose ties, as in Caulerpa {Y\g. 333), or by matting' of their branches together, as in Codium, or by cementing tho*«c branches together, as in Halimeda. But these are concessions to an essentially weak construction. It is only possible to carry it to any considerable size when hving in water, and all the larger forms are marine. Vanchevia is an exception : for though many of its species float in water, some live on moist soil, exposed to liie .or. But the members of the genus consist only of simple or filaments, and when living aerially they lie I-IG. 333. Part of a transverse section of Caulerpa, showing the thick outer wall, .mil the reticulate rods of cellulose, which act as ties, and give added rigidity. ( :< 50.) The cytoplasm of these plants contains many small chloroplasts. and numerous nuclei usually lying internally to them. Centrally is a large vacuole. In Vaucheria the product of appears as oil, but others of the Siphoneae may contain starch, which is commonly present in Green Algae. The general physiology of a coenocytic, or as it has been called a non-cellular plant, is probably like that of any ordinary green plant. The difference lies in ihc mechanical construction. Vegetative propagation is carried out in various Siphonaccous Algae by non-motile, or by motile cells, produced in large numbers in special branches, and liberated into the water. V\iucheria is an exception, in that the whole contents of such a branch-ending, which are previously shut off by a septum, are discharged as a single ciliated zoospove, large enough to be seen with the naked eye. The escape is effected in the early morning; after a period of movement the zoospore comes to rest, and germinates directly into a new plant. P
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