. Morphology of gymnosperms. Gymnosperms; Plant morphology. 202 MORPHOLOGY OF GYMNOSPERMS The single thick integument, forming a long and narrow micro- pylar tube, is at first homogeneous, but by the last of May three distinct layers have become differentiated. The outermost layer is a tissue of large, thin-walled cells with numerous mucilage cavities, and finally becomes the fleshy layer of the mature testa. The middle layer consists of small isodiametric cells, and later forms the stony layer of the testa. The innermost layer consists of large, loosely. 232 233 Figs. 232, 233.—Ginkgo biloba:
. Morphology of gymnosperms. Gymnosperms; Plant morphology. 202 MORPHOLOGY OF GYMNOSPERMS The single thick integument, forming a long and narrow micro- pylar tube, is at first homogeneous, but by the last of May three distinct layers have become differentiated. The outermost layer is a tissue of large, thin-walled cells with numerous mucilage cavities, and finally becomes the fleshy layer of the mature testa. The middle layer consists of small isodiametric cells, and later forms the stony layer of the testa. The innermost layer consists of large, loosely. 232 233 Figs. 232, 233.—Ginkgo biloba: diagrams of ovules showing the stony layer (s) between the outer (0) and inner (i) fleshy layers, and the collar (c); fig. 232, after the stony layer has become hard, but before the inner fleshy layer has become dry; the inner fleshy layer and the nucellus are shaded with lines; fig. 233, after the inner fleshy layer and nucellus have become dry and papery; X2. arranged, very thin-walled cells, which in the free portion of the integument are differentiated into two regions: the inner consisting of vertically elongated cells, a tissue restricted to the free portion of the integument; the outer consisting of transversely elongated cells, a tissue that extends the whole length of the ovule just within the stony layer. This inner tissue is at first delicate and watery, but soon becomes crushed and dry, forming in the mature testa a papery layer lining the stone and adherent to it (figs. 232, 233). This general structure of the testa is practically cycadean (p. 128). It has come to. 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; Coulter, John Merle, 1851-1928. Morphology of spermatophytes. Part I. Gymnosperms. Chicago, University of Chicago
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