1922] SPESSARD—LYCOPODIUM 309 
region, from which has developed a more or less dorsiventral 
protuberance which becomes cylindrical near its apex only. In no 
case were there found the two forms of body as described for 
L. Selago, namely, the cylindrical or ‘‘ninepin” form and the 
flattened form. All the specimens of the vertically growing pro- 
thallia of L. lucidulum might roughly be considered as shaped 
like a “ninepin” or an Indian club, but upon close examination 
it has been found that sex organs grow only on one side, the rhizoids 
opposite and lateral to them, and that the symmetry is distinctly 
dorsiventral. It is only when active growth is taking place that 
the apical region ever becomes cylindrical at all. Fig. 51 shows a 
longitudinal section through the apex of a prothallium such as that 
shown in figs. 15 or 49. This bilateral symmetry is present from 
the very beginning of the differentiation from the meristem tissue. 
If the prothallia grow upon the surface, however, they are dis- 
tinctly of the L. clavaiwm or L. annotinum type (figs. 33, 35). Even 
when growth continues after a subterranean prothallium has 
reached the surface, this growth produces an expanded portion 
which rests upon the ground (figs. 34, 37, 39). In other words, 
when the length of the vertical portion is eliminated so that the 
primary tubercle lies immediately beneath the prothallium, we 
have a type in no essential respect different from that of L. anno- 
tinum. Figs. 32 and 37 show prothallia semisurface and semi- 
subterranean in development. In many instances (figs. 25, 28) 
horizontal growth is solely below the surface, and it is not until 
near maturity that the apical point turns abruptly vertical. In 
such instances the prothallia are evidently of the L. annotinum 
type originally, and later change. 
In short, there are three methods of growth: one in which growth 
is entirely vertical; one in which growth is first vertical, then 
horizontal; and another in which growth is first horizontal and 
then vertical. In several instances growth was originally vertical, 
later assumed the horizontal, and still later resumed the vertical. 
While a prothallium of ZL. Selago has never been examined, I 
cannot see from the figures of BRUCHMANN any evidence of a typic- 
ally “conical’’ or ‘‘ninepin” shape for that species of prothallium. 
His fig. 32, plate VI, is the nearest approach to it, but the form is 
