. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. SM)¥^ Fia. 70.—Pitius ian'eio,showing flattened end of pollen tube before discharge into the egg; the two male cells are at the tip and above them, but not shown, are the nuclei of the stalk and tube cells: X 500.—After C'iiameeklain. Fig. 71.—Pinus Zaricio, showing end of pollen tube just before dischai'ge; the male cells (m, m) in this case are be- hind the nuclei («) of the tube and stalk cells ; s, starch grains ; the pit is evident at the extreme tip; x 500.— After Coulter. tained gametophyte rests in th
. Morphology of spermatophytes. [Part I. Gymnosperms]. Gymnosperms; Plant morphology. SM)¥^ Fia. 70.—Pitius ian'eio,showing flattened end of pollen tube before discharge into the egg; the two male cells are at the tip and above them, but not shown, are the nuclei of the stalk and tube cells: X 500.—After C'iiameeklain. Fig. 71.—Pinus Zaricio, showing end of pollen tube just before dischai'ge; the male cells (m, m) in this case are be- hind the nuclei («) of the tube and stalk cells ; s, starch grains ; the pit is evident at the extreme tip; x 500.— After Coulter. tained gametophyte rests in the cuplike depression at the apex of the nucellus during all this period. Dixon ^^ says that in Pinus silvestris the pollen tube is sent out into the nucellus as soon as the grain is deposited, and that it passes a year or even more in the upper region of the nucellus, disorganizing the adjacent tissue and producing irregular cav- ities. This seems to be true of Pinus Laricio also, whose pollen tubes we have found in the nucellus in June. Coker reports that in Taxodium distichum, however, the pollen tube, sent out immediately after pollination, penetrates to the archegonia without interruption. See Appendix. The pollen tube in Piwus begins to renew its penetration \ {' of the nucellus during ^Vpril, about a year after the mother cell entered upon the reduction division, the large tube nu- cleus enters the tube, where it is completely invested by starch grains, and at the same time the generative cell divides into. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928; Chamberlain, Charles Joseph, b. 1863. New York, D. Appleton
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