. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. CYCADALES 29 turgid end of the tube bursts and discharges its contents into the chamber, in whose liquid numerous sperms have been observed swimming. As the archegonium necks open into the bottom of this chamber, the sperms swim to them and pass down to the egg. Webber observed in Zamia as many as four sperms in a single neck. As the sperm passes into the cytoplasm of the egg Ikeno and AVebber both observed that the cytoplasmic mantle with its cili- ated band slips off, and is left in the peripheral region of
. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. CYCADALES 29 turgid end of the tube bursts and discharges its contents into the chamber, in whose liquid numerous sperms have been observed swimming. As the archegonium necks open into the bottom of this chamber, the sperms swim to them and pass down to the egg. Webber observed in Zamia as many as four sperms in a single neck. As the sperm passes into the cytoplasm of the egg Ikeno and AVebber both observed that the cytoplasmic mantle with its cili- ated band slips off, and is left in the peripheral region of the egg cytoplasm, the sperm nucleus moving alone toward the egg nucleus. Ikeno states that shortly before the entrance of the sperm the egg nucleus develops a cuplike depression, into which the sperm nucleus is re- ceived. In any event, the »^ \ latter imbeds itself in the former, and, according to Webber, remains distinct for a long time (Fig. 25). Ikeno claims that the sperm nucleus " dis- solves " within the egg nucleus, and that all nu- clear organization is lost, but it seems more likely that the same condition obtains as in Conifers, a condition which might very easily have escaped observation. The prominent devel- opment of the pollen tube as an absorbing organ suggests a question as to its original significance. Associated with ciliated sperms, which have devel- oped in close proximity to the egg, the function of the tube as a sperm carrier is reduced to a minimum, and in fact does not seem to occur in the Cycads. It is an interesting question, therefore, whether the pollen tube originated as an absorbing. Fia. 25.—Fertilization in Cyeads: A^ fusion of the nuclei in Cyms revoluta, t indicating the so-called trophoplasmic substance; B, fusion of the nuclei in Zamia integrifoUa, b being the discarded ciliated band, x 20; C, the male nucleus (mn) of Zamia integrifolia after slip- pingiromthe cytoplasmic sheath and ciliated band, x 66.—^, after Ikeno ; B an
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