316 
R. C. McLean. 
aiul other organs, while completely destroyed outside. Even could 
all other objections he disposed of, there would still remain the 
difficulty of accounting for their production from a morphologically 
interior surface. 
The weight of argument seems to be against viewing them 
as rhizoids of the prothallus, so that they may be dismissed as 
merely invading hyphee, in spite of the attractiveness of the other 
theory. Intermediate stages between the free living Lycopod 
gametophyte, and the enclosed prothallus of forms like Lepido- 
carpon, there may, most probably, have been, and there is no 
reason why one such stage should not have presented an appear¬ 
ance analogous to this, with rhizoids developed almost entirely 
within the spore coat. Some day such a stage may actually be 
found ; unless functional mutation took place suddenly from the free 
form to the entirely enclosed, intermediate stages being passed 
over. 
Our present prothallus, however, seems to represent a stage 
further in the reduction than the suggested hypothetical one, for it 
has no preserved rhizoids in the interior. Nevertheless, there still 
remain a few outside, as attested by little, tubular protuberances 
to be seen on one or two of the peripheral cells, which can only be 
the stumps of rhizoids. 
Very few other fossil Lycopodineous prothalli, exclusive of 
Lepidoccirpon —where the prothallus is not uncommonly found— 
have been described, and no specimen of that belonging to Botliro- 
dendron has previously been recorded. Scott in the “ Studies in 
Fossil Botany ” 1 has figured an irregular-looking megaspore of 
Lepidostrobus Veltlieimianus, which is partly open and is filled with 
a regular, parenchymatous mass of cells, more or less isodiametric, 
but capped by a patch of small-celled tissue. 
W. T. Gordon 2 has recorded two specimens, both belonging 
to the same species as that described by Scott, which has evidently 
been specially liable to good preservaton. In one of these, which 
appears to be a median vertical section, the spore is unopened, and 
presumably unripe. The interior is filled with a parenchymatous 
mass, as in Scott’s specimen, but the lenticular cap of small-celled 
tissue is much better developed, and recalls the appearance of the 
gametophyte in Seluginella, although there are no archegonia. In 
' Second Edition, 1908, Part I, p. 188, Fig. 77. 
2 Gordon. “ Annals of Botany,” Vol. XXIV, No. XCVI. Oct. 1910 
“ Transactions of the Botanical Society of Edinburgh.” and 
Vol. XXIII, 1908. 
