. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Green Plants. It mar be regarded as the phvlogenetic i, L t, O Ch Ian njdoniot tadex 17:) starting-point of the various lines of Chlorophyceous descent. The history of these is ahistory of the intercalation of a vegetative phase between two successive motile (Chlamy-domonadine) generations, these motile phases being retained for reproductive purposes aszoospores and gametes ; in the oogamous types the male gamete alone remains motile, andcons
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Green Plants. It mar be regarded as the phvlogenetic i, L t, O Ch Ian njdoniot tadex 17:) starting-point of the various lines of Chlorophyceous descent. The history of these is ahistory of the intercalation of a vegetative phase between two successive motile (Chlamy-domonadine) generations, these motile phases being retained for reproductive purposes aszoospores and gametes ; in the oogamous types the male gamete alone remains motile, andconstitutes in the Archegoniate series the last remaining representative of the Chlamydo-monadine cell. The co-existence within the limits of an undoubtedly natural genus of the mostprimitive form of gamogenesis (the conjugation of equal clothed gametes) with aganiogenosiswhich has the essential characteristics of true oogamy is also a feature of unique interest.(Blackman & Tansley, 02.) As the genus is of such importance it has received considerable attention from anumber of investigators, notably Goroschankin (90—91), Dill (95) and Wille (03).. Fig. 102. Colourless members of the Volvocacese. A—7), Polytoma uvella Ehrenb.; B,formation of daughter-cells; C, fusion of motile cells; D, zygote. E and F, Chlamydoble-pliaris brunnea France; F, division of cell. G, Tetrablepharis ylobuhis (Zach.) —F, after France, x 660; G, after Zacharias (from Wille). Two of the most interesting genera of the Chlamydomonadese arcBrachiomonas and Lobomouas. The first-named occurs only in submarinehabitats and possesses a cell-body furnished with five horns, all directed back-wards : one straight posterior horn, and four curved horns regularly disposedaround the antero-median part of the cell (fig. 101 A—F). These hornsare hollow outgrowths of the cell, the protoplast extending to their extremities,although the chloroplast generally does not. Lobom-onas has only been foundin freshwat
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