. The Encyclopædia britannica; a dictionary of arts, sciences, literature and general information. obosa—maybe taken to represent, within the Phaeosporeae, successive steps inthe advance from isogamy to oogamy. The Peridiniaceae have been included among Flagellata underthe title of Dinoflagellata. The majority of the species belong tothe sea, but many are found in fresh water. The thallus is somewhatspherical and unicellular, exhibiting a distinction between anteriorand posterior extremities, and dorsal and ventral surfaces. The wallconsists of a basis of cellulose, and in some cases readily b
. The Encyclopædia britannica; a dictionary of arts, sciences, literature and general information. obosa—maybe taken to represent, within the Phaeosporeae, successive steps inthe advance from isogamy to oogamy. The Peridiniaceae have been included among Flagellata underthe title of Dinoflagellata. The majority of the species belong tothe sea, but many are found in fresh water. The thallus is somewhatspherical and unicellular, exhibiting a distinction between anteriorand posterior extremities, and dorsal and ventral surfaces. The wallconsists of a basis of cellulose, and in some cases readily breaks upinto a definite number of plates, fitting into one another like the platesof the carapace of a tortoise; it is, moreover, often finely sculpturedor coarsely ridged and flanged. Two grooves are a constant featureof the family, one running transversely and another these grooves lie two cilia, attached at the point of meeting on thedorsal surface. The protoplast is uninucleate and vacuolate, andcontains chromatophores of a brownish colour. It is not clear that ALGAE 59. Fig. 4.—Phaeophyceae, variously magnified. A. Hahpteris, apical region. B. Chordaria sp., apical region showing so-called trichothallic growth. C. Dklyota sp., apical cells immediately after dichotomy. D. Culleria sp., margin of thallus showing trichothallic growth. E. Halidrys, apical depression with leading cell. F. Macrocystis ip., tubular elements from the medulla, with sieve-like transverse walls. G. Laminaria sp., hyphae with trumpet-like ends also from Elachislea sp., plurilocular sporanges. (.A. B, C, D, E, H, L. M, P, from Englcr and Prantl. by permission of WilhclQ, from Tlie Annals of Botany, by jjcrroission of the Clarendon Press; the brown colouring matter which is added to chlorophyll is identicalwith phycophaein; two varieties of it have been termed phycopyrrinand pcridinine. Certain species, such as Cymnodinium spirale, arecolourless and therefore saprophyti
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