McLean (13) in 1912, described the prothallus of 
Bothrodendron mundum trom a thin section of a coal- 
ball. The prothallus, which lies almost entirely outside 
of the spore, is composed of angular, elongated, paren- 
chymatous tissue. The specimen shows at least three 
archegonia—represented by egg-cavities. McLean inter- 
preted the prothallus as follows: “... it may be said 
that this specimen represents a stage in the reduction of 
the primitive free-living Lycopod gametophyte towards 
the condition obtaining in the ‘‘seed”* of Lepidocarpon. 
The prothallus was not produced until after the mega- 
spore had been shed. It developed outside of the spore, 
but remained attached to the spore-wall at its base, and 
in form resembled the prothalli of modern heterosporous 
ferns.’* (p. 818) 
Gordon (14) in 1910 described the prothallus of Lep- 
wdodendron Veltheimianus from two thin sections, one 
showing a single archegonium and a small amount of ad- 
jacent tissue, the other showing an unripe (i.e. an un- 
opened) spore completely filled with parenchymatous 
tissue which resembled to a considerable degree the ga- 
metophyte of Selaginella. Thus, in at least this species 
of Lepidodendron, the gametophytic development was 
endosporal and the archegonia developed at the scar in 
the spore wall, apparently not on a protrusion of the pro- 
thallus. 
The prothallus of Selaginella_Amesiana was endospo- 
ral and the evidence points to the fact that the arche- 
gonia were developed on a protruded part of the prothal- 
lus, that is to say, since no archegonia have been found 
in the prothalli of unopened spores, and some spores show 
early stages in the opening of the scar slit, presumably 
the archegonial stage was later than any of those stages 
which were preserved. 
The only feature which militates against the reference 
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