. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . oniclangium; n, nannan-driuni or dwarf male. Zoogonidia 389 anterior pole, which is colourless and sometimes extended to form a pro-tuberance, there is a circle of numerous short cilia. This unique zoogonidiumsometimes possesses a pigment-spot. Its exit from the mother-cell onlyoccupies a few minutes, since the rapid disappearance of the delicate vesicleenables it to swim quickly away. On coming to rest it attaches itself by itsanterior hyali
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . oniclangium; n, nannan-driuni or dwarf male. Zoogonidia 389 anterior pole, which is colourless and sometimes extended to form a pro-tuberance, there is a circle of numerous short cilia. This unique zoogonidiumsometimes possesses a pigment-spot. Its exit from the mother-cell onlyoccupies a few minutes, since the rapid disappearance of the delicate vesicleenables it to swim quickly away. On coming to rest it attaches itself by itsanterior hyaline end, loses its cilia and develops a cell-wall. From this pointonwards germination conforms to two very distinct types, although in bothtypes the cell formed directly from the zoogonidium remains as a differentiatedbasal cell. Freund has stated that zoogouidia can be produced in CEdogonium pluviale by trans-ferring the filaments from a cane-sugar solution to dilute Knops solution. They are oftenformed in numbers in both the spring and the autumn when CEdogonium--filaments arebrought from outside temperatures to the temperature of the Fig. 243. Formation and escape of the zoogonidium in (Edogoniumconcatenatum (Hass.) Wittr. x 27f> (after Him). Iii the first and most usual type of germination the fixed end of the cellputs out an organ of attachment, which may be simple (fig. 244) or branched(fig. 245 A, and E—H). The nature of this hapteron depends to a greatextent upon the particular species and so also does the degree of tumidity ofthe cell. In most species the basal cell is more or less tumid, but in a few itremains almost cylindrical. The hapteron is in some cases an attaching discand in others a simple or branched rhizoid. The protoplast extends into therhizoid and its branches, but as a general rule the chlorophyll does not. Thedisc-development is generally in those young plants which are attached toa definite substratum (fig. 244 D, E and H), wher
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