[SIR J. w. DAWSON] ON THE GENUS LEPIDOPHLOIOS S9 



(1) Habit of Growth and External Parts. 



Trees, but by no means the hu'gest in the coal forests; branching 

 dichotomously bat sometimes unequally, so as to produce branches ajjpar- 

 ently lateral. Branches usually stout, but, in some species at least, with 

 slender branchlets bearing the strobiles. These may either be spiral or 

 in two ranks, or irregularly disposed, often on thick branches. Fertile 

 branchlets or peduncles, when mature, dropping off and leaving rounded 

 scai-s depressed in the centre and with a raised rim. Leaves very long, 

 linear, with one rib forming a keel below. The leaves are articulated to 

 the oblong leaf-bases by broadly rhombic surfaces pointed at the lateral 

 ends, and with three dots, the central one of which marks the fracture of 

 the bundle of vessels passing up the middle of the leaf.' The leaf-bases 

 are strap-shaped, decurrent on the bark below, but so flat and so loosely 

 attached above that, on the full development of the leaf, they separate at 

 the upper ends from the bark and curve outward, so that the leaf-scar 

 becomes pendant and the leaves seem to be borne on flattened petioles 

 bending downward from their line of attachment. When the leaves have 

 separated, the permanent leaf-bases remain, giving a rugged and scaly 

 appearance to the stem. Finally, in dead or abraded stems, the leaf-bases 

 are entirely stripped off, and a smooth surface of bark remains, on which 

 are seen merely traces of the lines from which the leaf-bases have been 

 torn off, and spirally arranged pits or elliptical spots marking the points 

 of entrance of the bundles of vessels of the leaves into the stem. When 

 in this condition the branches, especially those bearing the marks of the 

 cones, assume forms to which the names Halonia and Bothrodendron have 

 been applied. The latter term has, however, been used by Grand'Eury 

 and Zeiller for trees which seem to bo different from JJejndophloios, but 

 which I have not seen, at least in well preserved specimens, in the Acadian 

 coal-fields. 



The above description will serve to explain the various views which 

 have been held as to the leaf-bases and scars of Lepidophloios. In young 

 and slender branches these are like those of IJepidodendron, but as the 

 leaves become developed, the leaf-bases split off from the stem and b end 

 downward, the leaves still remaining attached, but not inverted^' as some 

 have supposed. Their lower parts, however, become horizontal, or even 

 bend downward, and do not attain to an upward direction until the}' 

 have spread out to an inch or more from the stem. When the old stem 

 or branch in this condition is flattened, the leaf-scars appear at the lower 

 instead of the upper sides of th eaf-bases. (Fig. A., p. 60.) A flat- 



' The name " cushions," .sometimes applied to the leaf -bases, is quite inaccurate. 

 They are really flat, strap-like organs. 



2 Dr. Williamson, Proceedings Royal Society, Vol. Iv., No. 334, 1894 





