. The essentials of botany. Botany. 120 BOTANY. 252. The reproduction of desmids takes place by fission and by union; that is, asexually and sexually. In the first, the neck uniting the two halves of the cell elongates and becomes divided by a trans- verse partition, so that instead of the original —Ades- Symmetrical cell there are now two exceed- mldin process of . , , . , ,„. __v ., fission. Highly mgly unsymmetrical ones (.rig. 52); these grow by the rapid enlargement of the new and small halves; eventually the two cells become sym- metrical, by which time they have separated. This p
. The essentials of botany. Botany. 120 BOTANY. 252. The reproduction of desmids takes place by fission and by union; that is, asexually and sexually. In the first, the neck uniting the two halves of the cell elongates and becomes divided by a trans- verse partition, so that instead of the original —Ades- Symmetrical cell there are now two exceed- mldin process of . , , . , ,„. __v ., fission. Highly mgly unsymmetrical ones (.rig. 52); these grow by the rapid enlargement of the new and small halves; eventually the two cells become sym- metrical, by which time they have separated. This pro- cess may be repeated again and again. 253. In the sexual process each of two cells which are. Fig. 53.—Sexual reproduction of a desmid (Cosmarium menenghinii). a, front; 6, end; c, side view of the adult plants; d. two cells conjugating; e. young rest- ing spore formed; /. ripe resting spore, with spiny wall—the four halves of the parent cells are empty; g, the resting spore germinating after a period of rest; A, the young cell escaped fi-om resting spore; *' young cell dividing, showing two new plants, similar to a, placed crosswise in the interior of the cell. Magni- fied 475 times. near one another sends out from its centre a tube, which meets the corresponding one from the other {d, Fig. 53). At the point of meeting the two tubes swell up hemispherically, and finally, by the disappearance of the separating wall, the contents unite and form a rounded resting spore (e), which soon becomes coated with a thick wall (/). After a longer or shorter time the resting spore may germimte, Fio. 54.—A common desmid, Glosleiium. Highly Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bessey, Charles E. (Charles Edwin), 1845-1915. New York, Holt
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