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.

    97/160 (page 83)
    bn-ophytes has been designated “progressive steril- ization,” and its general result was to increase sterile tissue, by means of which a more and more complex body could be organized, and correspondingly to decrease sporogenous tissue, so that this tissue finally came to be a veiy insignificant part of the body in amount, and appeared only relatively late in the development of the body. The whole impression one gets from this prog- ress is that the sporophyte is developing more and more as a distinct individual, with body-regions and organs. The most important fact in the history of the sporo- phyte through the biyophytes, after the general fact of progressive sterilization, is that the sporoi)hyte of certain liverworts began to achieve indejiendence. In most biyophytes the sporophyte is absolutely depend- ent upon the gametophyte, but the sporophytes of the liverworts referred to develop green tissue, which means that, although they are anchored in the gametophyte and secure food from it, they are still able to manu- facture food for themselves. If these green sporophvtes could establish connections with the soil they would become absolutely independent, and cea.se to belong to br}'ophytes. The future of the sporophyte, there- fore, was to achieve independence from the gametophyte, and this independence was begun by this group of liver- worts and established by the pterido])hytes. before describing the great change in the character of sporophytes and gametophytes among the pterido- phytes, it may be well to consider what may be called the failure of br\’ophytes, since it probably has some- thing to do with the modifications of the two genera- tions that characterize the pteridophytes. by failure