. Text-book of botany, morphological and physiological. Botany. 254 THALLOPHFTES. In Pandorina Morum (Fig. 167) the complete course of development was followed by Pringsheim, this being the first instance that had been observed of the conjugation of zoogonidia. Pandorina is one of the commonest of the Pandorineae. The sixteen cells of a ccenobium (Fig. 167, 7) are closely crowded together, and surrounded by a thin gelatinous envelope out of which the long cilia protrude. The non-sexual multipli- cation results from each of the sixteen cells breaking up into sixteen smaller cells; the sixteen d
. Text-book of botany, morphological and physiological. Botany. 254 THALLOPHFTES. In Pandorina Morum (Fig. 167) the complete course of development was followed by Pringsheim, this being the first instance that had been observed of the conjugation of zoogonidia. Pandorina is one of the commonest of the Pandorineae. The sixteen cells of a ccenobium (Fig. 167, 7) are closely crowded together, and surrounded by a thin gelatinous envelope out of which the long cilia protrude. The non-sexual multipli- cation results from each of the sixteen cells breaking up into sixteen smaller cells; the sixteen daughter-families (II) become free by the absorption of the gelatinous envelope of the mother-family ; each daughter-family, again surrounded by a gelatinous? envelope, grows to the original size of the mother-family. The sexual reproduction. FIG. 167.—Development of Pandorina Morum (after Pringsheim); la swarming family; //one divided into sixteen daughter-families; /// a sexual family, the separate cells emerging from the gelatinous envelope; IV, V conjugation of the zoogonidia; VI a zygospore just formed ; VII a mature zygospore; VIII transformation of the contents of a zygospore into a large zoospore; /^ffree zoospore ; X young family produced from the last. is brought about in exactly the same way, but the gelatinous envelopes of the young families become softened, and the separate cells are thus freed and each swims about by itself (ill); these free zoogonidia are of very variable size, rounded and green at the posterior end, pointed, hyaline, and furnished with a red corpuscle in front, where they bear the two cilia. Among the crowd of these zoogonidia may be seen some which approach in pairs as if they were seeking one another. When they meet, their points come in contact, and they coalesce into a body at first hour-glass-shaped (IF), but gradually contracting into a ball (F); in this ball the two corpuscles and the four cilia at the enlarged hyaline spot are still to
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
