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

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

Licence: In copyright

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

    85/160 (page 71)
    probably indicating that there were formerly in the history of the archegonium two or more rows of gamete- forming cells within the sterile jacket. In any event, the fact of the transformation of the game- tangium of algae into the arche- gonium of liverworts as a result of exposure to aerial conditions seems to be well assured. The archegonium is a very characteristic and persistent organ, changing comparatively little throughout its whole history. So constant is it that the groups which develop it, namely, the bryophytes (liverworts and mosses), pteridophytes (ferns, club mosses, etc.), and gymnosperms (conifers, etc.), are called collec- tively archegoniates, as distin- guished from the thallophytes (algae and fungi) below, and the angiosperms (flowering plants) above, which do not have arche- gonia. This is an evidence of the remarkable adjustment of the archegonium as a sex organ suit- able for land plants. The same statement may be made in general in reference to the antheridia that accompany the arche- gonia through most of the archegoniates. They vary more in details of development than do the archegonia, Fig. 29.—The anthe- ridium of a pine, repre- sented by cells (or nuclei) developed within the pollen grain; in the figure, the pollen tube has begun to develop, and one of the anthe- ridial nuclei has passed into it.