. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PRESENT POSITION OF PALEOZOIC BOTANY SCOTT. 383 1 or even 2 mm. in diameter. Both are tetrahedral in form. At a point corresponding to the apex of the tetrahedron the mega spore, in most cases, oj)ened by flaps, often highly developed, forming a pas- sage, through which, presumably, fertilization was effected. The jDrothallus within the megaspore of Lepidostrohus is occasionally found preserved, and the archegonia have even been recognized.
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PRESENT POSITION OF PALEOZOIC BOTANY SCOTT. 383 1 or even 2 mm. in diameter. Both are tetrahedral in form. At a point corresponding to the apex of the tetrahedron the mega spore, in most cases, oj)ened by flaps, often highly developed, forming a pas- sage, through which, presumably, fertilization was effected. The jDrothallus within the megaspore of Lepidostrohus is occasionally found preserved, and the archegonia have even been recognized. The cones of Sigillaria {Sigillariostrohus) also are heterosporous. In the cones known as Spencerites the large sporangium is attached to the bract or s]3orophyll only at its distal end by a narrow enervate neck. The spores are furnished with a very characteristic wing, which probably aided in dispersal. The most interesting, however, of the Paleozoic Lycopodineous fructifications are those which show a near approach to the produc- tion of seeds. At present two gen- era are known in which the mega- "' sporangium assumed a seed-like character—Lepidocarpon and Mi- adesmia. In Lepidocarpon the an- atomy and morphology of the megasporangiate cone, in its young condition, are in all respects those of an ordinary Lepidostrohus. The megasporangia are attached, in the usual manner, to the upper surface of the sporoph^dls, which are provided with ligules, as in Lepidostrohus. The palisade struc- ture of the sporangial wall is also the same as in that genus. In each megasporangium, however, only a single megaspore came to perfection, filling practically the whole cavity, like an embryosac; its three sister cells can often be detected in an abortive condition. At maturity the megasporangium was inclosed in an integument (fig. 5), springing from the upper surface of the sporophyll, and forming a complete investment to the sporangium, except for a narrow crevice along the top, comi^
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