234 Boodle. — On the Production of Dwarf Male 
appear to be incapable of bursting the wall of the sporangium, and they 
and the ungerminated spores ultimately die. Several attempts were made 
to obtain motile spermatozoids, but always failed. Sporangia were ruptured, 
and the contents examined in water, but usually any antheridia present 
refused to burst. Once or twice an antheridium was seen to dehisce, and 
the spermatocytes passed out, but the spermatozoids did not even uncoil. 
Free spores, when germinated in the light, formed normal prothalli 
(see Fig. n), which, however, showed some differences according to the 
nature of the culture. On sand the primary rhizoid was usually long ; on 
damp blotting-paper it was often well developed, but sometimes rudimentary 
or absent ; in water it was often rudimentary or absent, though occasionally 
fairly well developed. On blotting-paper reduction of most of the rhizoids 
was sometimes observed, and appeared to be caused by wetness of the 
culture. In water the prothallus tended to be more rounded, or thicker 
and less elongated, than on sand or blotting-paper. 
In most cases free spores were found to germinate very readily in the 
light. Direct sunlight was kept off the cultures by a screen, and a blind 
on the top of the greenhouse reduced the light. From an experiment in 
which the light was further reduced and growth less rapid, one may assume 
that, if the illumination was above the optimum, it was not far above it 1 . 
The spores are also capable of germination in darkness, but growth is 
slower than in light, and finally comes to a standstill. Figs. 5 and 6 are 
from two cultures of T. Fraseri after twenty-six days in darkness. Fig. 5 
is a prothallus and antheridium from a closed sporangium, and Fig. 6 is 
a prothallus formed by the germination of a free spore. In Fig. 5 the 
sperm-cells ( s .) are shown in the antheridium, and the greater part of the 
prothallus is enclosed in the exosporium ( e .), so that it cannot be seen how 
many cells are present. This experiment shows that light is not necessary 
to the production of antheridia inside the sporangium. Gametophytes with 
antheridia, similar to Fig. 5, were formed in several sporangia in darkness^ 
and, just as in cultures in the light, they were accompanied by some small 
prothalli without antheridia. A rather common feature in sporangia kept 
in darkness is the presence of prothalli with abortive antheridia, and what 
may be described as vegetative transformations of young antheridia. These 
will be referred to again later. Fig. 7 is one of the most reduced gameto- 
phytes met with, and is from a sporangium after twenty-two days in 
darkness. The antheridium has a very small cavity ( a .), below which there 
are only two cells, one probably representing the stalk, and the other the 
prothallus. 
In T. hy 7 nenophylloides the germination of the spores and the growth 
of the prothallus are less rapid than in T. Fraseri under the conditions of 
1 Heim (’96, p. 354) found that for certain Fern-prothalli the strongest growth took place in 
daylight (Munich) reduced by 20-25 P er cent. 
