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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    the overla])j)ing regions of physics and chemistry. Nor can it be true that gametes are peculiar in containing the factors of heredity, for these must have been handed down through all the cell generations leading to the gametes. Ciametes furnish the opportunity for heredity to exjjress itself, but so do spores, and so does vegetative multiplication. If gametes are peculiar in the construction of their nuclei, how do they develop this peculiarity ? The evidence given in the preceding chapters seems to make it clear that this gametic peculiarity, whatever it may be, is developed in connection with the reduction division. Among plants this division occurs generally in connection with spore-formation, and when there are no spores, as in Fucus, it occurs in connection with gamete-formation, as in animals. In case the reduction division fails in connection with spore-formation, it has been observed that the resulting 2X egg is unable to fuse with the sperm. If fusion is made possible by the presence of the mutually attractive substances referred to, it would seem that these also may be developed in connection with the reduction division. In any event, the reduction division determines the sexual condition, and the peculiarity of this division as compared with ordinary division is related to the peculiar constitution of the nuclei of gametes as compared with other nuclei. If gametes have any structural peculiarity, it must be developed in connection with this peculiar nuclear divi- sion. In well-balanced alternation of generations, as in biy’ophytes and pteridophytes, there are many cell generations between spores and gametes, and how the peculiarities of the gametes are transmitted through