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 megaspore, in 
most cases, opened by flaps, often highly developed, forming a pas- 
sage, through which, presumably, fertilization was effected. The 
prothallus within the megaspore of Lepidostrobus is occasionally 
found preserved, and the archegonia have even been recognized. 
The cones of Sigillaria (Sigillariostrobus) also are heterosporous. 
In the cones known as Spencerites the large sporangium is attached 
to the bract or sporophyll 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 Lepidostrobus. 
The megasporangia are attached, 
in the usual manner, to the upper 
surface of the sporophylls, which 
are provided with ligules, as in 
Lepidostrobus. The palisade struc- 
ture of the sporangial wall is also 
the same as in that genus. In Fic. 5.—Lepidocarpon Lomazi. Diagram- 
each megasporangium, however, matic section of Seu organ cut in 
a plane tangential to the parent strobilus. 
only a single megaspore came to sph, sporophyll; v. b, vasular bundle; i, 
perfection, filling practically the integument 8 micropylar crevice ; sm, 
: ; wall of sporangium; a, insertion of 
whole cavity, like an embryosac;  sporangium on sporophyll; mg, mem- 
its three sister cells can often be rane of megaspore or embryo-sac; pr, 
detected in an abortive condition, Pon ™® TRE Mesaspore. 
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, comparable to a micropyle, but of great length, corre- 
sponding to the radial elongation of the sporangium. Within the one 
functional megaspore a prothallus was developed, which is sometimes 
excellently preserved, and was already present in the earlier stage of 
the megasporangium before the integument had been formed.. The 
sporophyll, with its integumented megasporangium, was shed entire, 
and appears to have been indehiscent. The analogies with true seeds, 
m 
