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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    and certainly they do not multiply individuals. They are the same individual in an inactive condition, no new individual being j)roduced. In both of these cases the behavior of the protoplast is in response to conditions unfavorable to vegetative activity. 'The same kind of response appears in ordinary spore- formation, in which the protoplasts become freed from the wall, round ofT, and are entirely detached from the general life of the individual producing them. In many algae and fungi it is entirely possible to control spore-formation experimentally. In other words, con- ditions can be supplied which inhibit spore-formation indefinitely, and other conditions can be supplied which stimulate abundant spore-formation. In general, what- ever diminishes vegetative activity favors spore- formation, so that it is the physiological condition of the protoplast that determines whether it continues to do vegetative work or becomes a spore. It is well to em])hasize this fact, because there is a general impression that spore-formation de])ends upon a certain amount of maturity in the plant, in other words, that plants pro- duce spores “when the time of spore-formation comes.” It is true that the time of spore-formation is measurably uniform in the histor>^ of a given plant, but this simply means that the condition of spore-formation is meas- urably uniform in making its appearance. If it should appear earlier or later than the usual time, spore- formation will occur in spite of the time. The sus- picion is that the favorable condition that induces spore-formation experimentally is represented in nature by the waning activity of the plant. Regular periods for spore-formation furnish abundant testimony to the