The evolution of sex in plants / by John Merle Coulter.

  • John Merle Coulter
Date:
[1914]
Catalogue details

Licence: In copyright

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

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    without affecting reproduction. What may be called the first stage in the evolution of asexual reproduction, therefore, is represented by those one-celled plants whose only method of reproduction is ordinary cell division, which is a function exercised by any protoplast under appropriate conditions. When plants become many-celled, ordinary cell division does not result in new individuals; that is, ordinary cell division and reproduction are not synony- mous. The result of cell division is not new indi- viduals, but the growth of the same individual. In other words, cell division has become a feature of growth. In this situation, therefore, the most primitive form of reproduction has come to express itself in the growth of a single individual. This transition from cell division resulting in new individuals, to cell division resulting in growth, has established, or at least has become chiefly associated with, a new form of asexual reproduction. Before describing this, however, attention should be called to the fact that in many-celled plants certain cells may appear to have lost the power of division, while other cells have retained it. This association of protoplasts in the individual, therefore, has not only modified the form of asexual reproduction, but has resulted apparently in the loss of the power of division by certain protoplasts. An analysis of the facts may modify this impression somewhat. As a rule, a meri- stematic cell, that is, one that divides, usually does so when it is young. If for any reason it becomes relatively old without dividing, it seems to have lost the power, and never divides, becoming a permanent cell, as con- trasted with a meristematic one. With such facts under
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