. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 502 FILICALES this species that the incipient stages of germination have been observed within the sporangium, a fact held to show its Fern-nature, while its other characters relate it to the Botryopterideae. The sporangia have been successfully observed in Zygopteris by Renault (Fig. 272). They were borne in groups on the ends of the pinnules, and were pear-shaped and slightly curved. The stalk, though elongated, was fairly robust, and widened gradually into the sporangial head. The latter was compose
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 502 FILICALES this species that the incipient stages of germination have been observed within the sporangium, a fact held to show its Fern-nature, while its other characters relate it to the Botryopterideae. The sporangia have been successfully observed in Zygopteris by Renault (Fig. 272). They were borne in groups on the ends of the pinnules, and were pear-shaped and slightly curved. The stalk, though elongated, was fairly robust, and widened gradually into the sporangial head. The latter was composed of at least two layers of cells, the inner of which was. Fig. 271- Stauropteris Oldkamia, Binney. A ~sporangium in nearly median section, attached terminally to an ultimate hranchlet of the rachis ; $£=stomium. Scott. Coll., 2213. .6' = sporangium in tangential section attached to a short piece of a branchlet. Scott. Coll., 2207. C = sporangium with wall burst attached as before. / = palisade tissue of branchlet. Scott. Coll., 2219. All figures xabout 50. (From sketches by Mrs. D. H. Scott. 1'he specimens are from Shore, Littleborough, Lanes.). transient, while the outer remains as the mature sporangial wall. This is differentiated to form the annulus, which appears as a broad band composed of several rows of deep cells, with indurated walls, and ran along either side of the sporangium from base to apex; the remainder of the wall is composed of smaller, elongated cells. The mechanical annulus thus composed of several rows of cells, forming a broad marginal band or hoop, resembles the similar structure seen in the sporangium of Augiopteris (see below, pp. 515-16). The spores are numerous : a rough estimate from the transverse and longitudinal sections drawn by Renault points to an output of 500 to 1000 spores in each full-sized sporangium : but there is considerable variation in the dimensions of the Please note that these images are extracted from scanned page im
Size: 1826px × 1369px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherlondonmacmillanand
