. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 302 LYCOPODIALES borne by the megasporophyll. So far as it goes, then, the evidence from the fossils favours the conclusion that plants resembling Selaginella existed in the primary rocks, and that even the more specialised heterophyllous type of Selaginella dates at least from the Carboniferous period, while it seems possible that a seed-like habit had already been established. The dendroid Lycopodiales are among the earliest known fossils, dating from the Lower Devonian period to the Trias. They inc
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. 302 LYCOPODIALES borne by the megasporophyll. So far as it goes, then, the evidence from the fossils favours the conclusion that plants resembling Selaginella existed in the primary rocks, and that even the more specialised heterophyllous type of Selaginella dates at least from the Carboniferous period, while it seems possible that a seed-like habit had already been established. The dendroid Lycopodiales are among the earliest known fossils, dating from the Lower Devonian period to the Trias. They include the families of the Lepidodendraceae, Bothrodendraceae, Sigillariaceae, and. Fig. 150. Ground plan of a Tree-stump with Stigmaria-trunks. One-sixtieth the natural size. (After Potonie.) Pleuromoiaceae. Underlying the differences of detail according to which these families are distinguished, there is a general unity of morphological plan: the essential features of it are as follows. The main axis was upright, rising in some cases to a height of 100 feet. It was bulky relatively to the numerous simple leaves which it bore: it branched upwards in a dichotomous manner, in most cases profusely: in some of the Sigillariaceae, however, and in Pleuromoia branching may be entirely absent. The development of the branches of the dichotomy were in various cases either equal or unequal, a fact which leads to differences of habit, as is seen to be the case in Lycopodium or Selaginella. The axis was fixed in the soil by a shallow and broadly spreading system of Stigmarian trunks (Fig. 150). In Lepidodendron the main Stigmarian trunks usually numbered four, which bifurcated repeatedly, thus forming a. 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. ,
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