. Plant life, considered with special references to form and function. Plant physiology. SEXUAL REPRODUCTION. 271 may round itself off and, alone, become a resting spore. These resting spores, after a dormant period, germinate and develo]) into new ijlanis. In Ulothrix, tlierefore, the gametes are imperfectly sexual. Failing to conjugate, as many do, they may still dexelop into new individuals. A con- sideration of the apjjearance and behavior of the gametes leaves little doubt that they are merely small zoospores which have acquired imper- fectly the habit of conjuga- tion and retained partia
. Plant life, considered with special references to form and function. Plant physiology. SEXUAL REPRODUCTION. 271 may round itself off and, alone, become a resting spore. These resting spores, after a dormant period, germinate and develo]) into new ijlanis. In Ulothrix, tlierefore, the gametes are imperfectly sexual. Failing to conjugate, as many do, they may still dexelop into new individuals. A con- sideration of the apjjearance and behavior of the gametes leaves little doubt that they are merely small zoospores which have acquired imper- fectly the habit of conjuga- tion and retained partially the power of independent growth. 374. Further develop- ment.—The perfecting of reproductive methods fol- lowed the two lines just sug- gested. On the one hand, y complete sexuality was ac 302.—.Sporelings of I'U-'tJirix zoiiata. quired by certain cells, while «. a young plant" from a large zoospore. /', young plants from small zoospores whiclt others were more COmpletelv germinated without leaving the mother cell. INIagnihed 4S2 diam.—After Dodel-Porl. specialized as non-sexual re- productive bodies. The latter ha\e already been discussed (1l3°4ff.)- Tracing now only the line of sexual development, it is probable that the first step in this differentiation was the failure of some of the zoospores to escape irorn the cell pro- ducing them. From this point two lines of development diverge. 375. I. Isogamy.—Along one of these lines, the zoo- spores ceased to form cilia, and became non-motile sex cells, in some cases similar in form and function, and in others. 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 Barnes, Charles Reid, 1858-1910. New York, H. Holt & company
Size: 1326px × 1884px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectplantphysiology
