. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . female gametes are about three times the size of the male gametes,possessing a rather large posterior chloroplast with one pyrenoid and apigment-spot. The male gametes, which are of a brownish-red colour, haveonly a very small chloroplast and no pigment-spot. The paired cilia are in Derbesiacex each case attached to the anterior pointed end. The fusion of the gametes(vide fig. 146 3 and 5 a) results in a rounded zygote which is capab
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . female gametes are about three times the size of the male gametes,possessing a rather large posterior chloroplast with one pyrenoid and apigment-spot. The male gametes, which are of a brownish-red colour, haveonly a very small chloroplast and no pigment-spot. The paired cilia are in Derbesiacex each case attached to the anterior pointed end. The fusion of the gametes(vide fig. 146 3 and 5 a) results in a rounded zygote which is capable ofimmediate germination. The Bryopsidacete are closely related to the Derbesiaceae and the Codiacese ; they occurin all seas, but more abundantly in the warmer oceans. The genera are : Bryopsis Larnouroux, 1809 ; Pseudobryopsis Berthold, 1880. Family Derbesiaceae. This family includes the single genus Derbesia first described by Solierin 1847. In general habit the thallus is tufted, numerous erect and more orless cylindrical branches arising from narrower, creeping rhizome-likebranches, which are fastened to the substratum by branched holdfasts. Fig. 147. 1 and 3, Derbesia Lamourouxii (J. Ag.) Solier. 1, general aspect, iiat. size;3, rhizome and bases of shoots, x 5. 2,4 and 5, D. marina (Lyngb.) Kjellm. 2, bases ofbranches; 4, zoogonidangium ; 5, zoogonidium. (From Oltmanus ; 2, after Kjellman ; 4,after Kuckuck ; 5, after Solier.) ( 1\ The whole thallus is the development of a single coenocyte,but the erect branches are often separated at the base by double cell-wallsresulting in the formation of a small basal segment (fig. 147 2). There isno differentiation into stem and leaves, if one excludes the zoogonidangiawhich are homologous with the leaves of Bryopsis, and the erect tubularbranches have a great resemblance to the filaments of a thick cell-wall is thin and not encrusted. In the older parts of the thallusa few transverse walls may sometimes
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