Evolution of sex in plants / by John Merle Coulter.

  • Coulter John Merle, 1851-1928.
Date:
[1914]
Catalogue details

Licence: In copyright

Credit: Evolution of sex in plants / by John Merle Coulter. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    which would have eliminated asexual reproduction if it was eliminated at all among plants, reproduction by tubers, bulbs, and cuttings, as well as the universal occurrence of microsi)ores (pollen grains) and mega- spores, testify to the fact that asexual reproduction is not even a declining method. It is also among jdants that the origin of the sexual method is in evidence. It did not appear as an entirely new mechanism, detached from everything that pre- ceded it, but arose as a gradual modification of one of the asexual methods; nor did it appear at first with all the significance it attained later. This seems obvious enough, even if the significance of sex in each step of its ])rogress cannot be explained. If sexual reproduction has arisen from asexual reproduction, it is necessary to trace the evolution of the latter, at least to the point where sex appeared. In doing this no effort will be made to specify the plants that contribute the evidence. They are sufficiently known to botanists, and would be meaningless names to those who are not botanists. The series of facts herewith presented, however, should be clear enough to all. The use of the term “reproduction” in this dis- cussion must be defined. Any cell that produces another one is performing the function of reproduction, but the result may be merely the growth of an indi- vidual, or the restoration of wasted tissue, or the healing of a wound. It is obvious that such results are not included in reproduction as currently understood. As ordinarily applied, and as it will be applied here, it means the production of new and independent indi- viduals that become self-supporting.