462 
VASCULAR CRYPTOGAMS, 
inner and an outer cell, so that at this stage the young prothallium consisted of four 
short cells forming an axial row terminated above by the apical cell, below by the 
basal cell, and enclosed laterally by two rows of cells. It was impossible to trace 
the development any further. Fifteen years later (1872) Fankhauser found in 
Switzerland completely developed prothallia of Lycopodium annotinuni among some 
Mosses, one of which was still connected with the young plant of the second 
generation (Fig. 326). These prothallia, which had grown in the absence of light, 
were irregularly lobed masses of cells of a pale yellow colour, furnished sparingly 
with small root-hairs. On the upper surface were numerous antheridia which are 
ovoid cavities in the tissue of the prothallium covered by a single layer of cells and 
filled with the very numerous mother-cells of the anthero- 
zoids. The form of the antherozoids themselves was not 
very clearly made out. These prothallia had no longer 
any archegonia, but they bore young plants : hence it ap- 
pears that Lycopodium produces only one kind of spores, a 
conclusion which is quite in accordance with the results of 
direct observation, and that the prothallia are monoecious, 
a peculiarity which at once sharply distinguishes the Lyco- 
podiceae from the Isoeteae and Selaginelleae, as does also 
the very considerable size attained by the prothallium and 
its complete independence of the spore. Probably these 
conditions are the same in those genera which possess but 
one kind of spores, Psilohim, Tmesipteris, Phylloglossuin. 
The prothallia of Lycopodium evidently bear several arche- 
gonia, for Fankhauser found on them young plants in 
various stages of development. From the attachment of the 
young plant to the prothallium, it appears that the arche- 
gonia lie upon its upper surface in the grooves between the 
lobes. 
2. The Asexual generation (Sporophore). From what has 
already been said it is evident that nothing is known con- 
cerning the development of the embryo. The young plants 
which Fankhauser found were attached to the prothallium 
by means of a small projection, about the size of a pin's 
head inserted into its tissue. This projection arises at the 
side of the base of the stem and of the first root ; it evidently corresponds to the foot 
of Ferns. 
The habit of the mature pla.nts is very various in the different genera. Some 
species of Lycopodium have an erect stem and erect branches (Z. Selago), in which 
case the roots arising from the lower part of the stem often grow downwards within 
it and issue in a tuft from its base [L. Phlegmaria^ ulici/oliujji, Sec). Very frequently 
the main stem and its largest branches creep upon the earth, sending out roots here 
and there into the soil, only certain branches, more especially those which bear the 
sporangia, being erect. In these forms there is a tendency towards bilateral 
organisation, which finds expression more particularly in the structure of the axial 
fibrovascular mass. In all species the stem is thickly covered with small, narrow, 
FIG. 326. — Lrcofodiimi aniio- 
tinum, after Fankhauser; p the 
prothallium, / the young plant ; 
■w its root (natural size). 
