Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/379

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The Cycas revoluta figured in Pl. 58 possesses a peculiar interest in relation to both our fossil species, in consequence of its protruding a series of buds from the axillæ of many of the scales around its trunk. These buds explain analogous appearances at the axillae of many fossil scales on Cycadites

trunk towards the leaf. On the lower integument, (b') is a dense coating of minute curling filaments of down or cotton, (a) which being repeated on each scale, renders the congeries of scales surrounding the trunk, impervious to air and moisture.

A similar disposition is seen in the longitudinal section of the fossil Petiole of Cycadites microphyllus represented at Pl. 62, Fig. 2, and magnified four times. At a we have cellular tissue interspersed with gum vessels, h. Beneath c, are longitudinal bundles of vessels; at b, is the integument; at a, a most beautiful petrifaction of the curling filaments of down or cotton, proceeding from the surface of this integument.

In the vascular bundles within the fossil Petioles, (c) Mr. Brown has recognised the presence of spiral, or scalariform vessels (Vasa scalariformia) such as are found in the Petioles of recent Cycadeæ; he has also detected similar vessels, in the laminated circle within the trunk of the fossil Buds next to be described. The existence of vessels with discs peculiar to recent Cycadeæ and Coniferæ, such as have been described in speaking of fossil Coniferæ, has not yet been ascertained.