TNTRODUOTION TO CRYPTOGAMIC BOTANY. 563 



there can be little doubt that Dr. Hooker is right in consider- 

 ing them highly developed Lycopodia. The stem, for exam- 

 ple, of Lepidodendron consists of a central mass, composed 

 principally of large scalariform vessels, giving off branches, 

 which traverse a mass of thick walled cells to the scars of the 

 leaves ; while that of Sigillaria has wedges of vascular tissue, 

 interrupted by rays passing from the surrounding cellular 

 tissue to the centre. Sigillaria, then, is merely a form allied 

 to Lepidodendron approaching still more closely the structure 

 of Phtenogams. In Stignn,aria the bundles arise from ducts 

 seated nearer to the centre than the wedges ; in Sigillaria, 

 on the contrary, they arise partly from the outer margin or 

 convexity of the wedges, partly from the inner margin or angle 

 of the wedge, the fascicles uniting in front before they enter 

 the leaves. Stigmaria has been shown by Dr. Hooker to be 

 merely the roots of Sigillaria, and the connection of Lepido- 

 strobi with Lepidodendron is no less certain. The stems of the 

 latter differ principally from Lycopodium in size, and so the 

 cones of the former differ in their greater development, and in 

 the thickness of the'scales approaching those of Conifers. The 

 spores of Lepidostrohus ornatus, as figured by Dr. Hooker, 

 are spherico-tetrahedral, just like those of Lycopodium. 

 Three spores are sometimes formed from the same mother cell 

 adhering by their triangular faces, and sometimes four, so that 

 the Triplosporite* of Brown does not seem to be generically 

 different from Lepidodendron. However similar the cones 

 may be to those of Conifers, or however enormous the sporan- 

 gia in comparison of those of recent Lycopods, it must be 

 remembered that they are sporangia still, and that their con- 

 tents are spores, often much smaller than in any modern club- 

 mosses. There is much reason to believe that the curious 

 fruits described by Dr. Hooker in the Proceedings of the Zoolo- 

 gical Society, 1855, p. 562, 566, are closely allied, though 

 possibly belonging to a distinct natural order. The fructifying 

 bodies seem clearly to be spores, but they are very different in 

 the two genera ; in the one approaching those of ferns, in the 



• Linn. Tr., vol. 20, p. 469. 

 36 * 



