. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. OF PSILOTACEAE 147 Sphenophyllaceae raise important questions. Among the former, Tmesipteris bears appendages of simple form in the vegetative region ; but the fertile appendages are forked at their distal end, and bear on their upper surface, just at the point of branching, a bilocular synangium, which has a short stalk traversed by a vascular strand (Fig. 77). Various views have been propounded in order to read this body in terms of the formal morphology of the higher plants: for us, the suggestion
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. OF PSILOTACEAE 147 Sphenophyllaceae raise important questions. Among the former, Tmesipteris bears appendages of simple form in the vegetative region ; but the fertile appendages are forked at their distal end, and bear on their upper surface, just at the point of branching, a bilocular synangium, which has a short stalk traversed by a vascular strand (Fig. 77). Various views have been propounded in order to read this body in terms of the formal morphology of the higher plants: for us, the suggestion would seem to suffice that. Fig. 76. Sficitceritcs insignis. Somewhat diagrammatic radial section of part of the cone, showing two sporophylls in connection with the axis. On the lower sporophyll the sporangium is shown attached at its distal end to the ventral outgrowth of the sporophyll : within the sporangium some of the characteristic winged spores are shown. (After Miss Berridge.) From Scott, Progresses rci Botanzcae, vol. i. the plant is heterophyllous, the vegetative appendages being simple and the fertile branched : while to the upper surface of the branched sporophyll a sporangiophore is attached with vascular supply and bearing two sporangia. In Psilotum the structure is the same, but the number of the sporangia is larger. The disposition of the parts in Sphenophyllum majus is again very similar to this (Fig. 78): a synangial group of four to six sporangia occupies a position comparable to that of the Psilotaceae on the upper surface of a doubly branched appendage ; but these appendages are disposed. 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 Bower, F. O. (Frederick Orpen), 1855-1948. London, Macmillan and Co. , Ltd.
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