232 Boodle.— On the Production of Dwarf Male 
product of germination of a single spore in the same sporangium. The 
antheridium at the top contains numerous sperm-cells (j-.), and is borne by 
an extremely reduced gametophyte, enclosed at the base by the ruptured 
exosporium ( e .). Below the cavity of the antheridium there are only five 
cells. Of these the upper two may be regarded as forming the basal part 
or stalk of the antheridium, thus leaving only three cells for the prothallus. 
No rhizoid-cell is present in this specimen. 
In the sporangium shown in Fig. 1, nearly all the spores had produced 
dwarf male prothalli similar to Fig. 2, but in other cases the number of 
male prothalli in a sporangium was usually small. For a typical case, in 
which intrasporangial germination has taken place and advanced sufficiently, 
the contents of the sporangium may be described as follows : a few pro- 
thalli of about three cells and usually with a rhizoid ; a few prothalli 
bearing antheridia, and nearly always without developed rhizoids ; the 
majority of the spores showing no signs of germination. In sporangia in 
which only two or three spores had germinated, the young prothalli had 
no antheridia, and usually bore rhizoids. From the presence of rhizoids, 
and from comparison with experimental cultures, in which germination has 
not advanced very far, one may infer that the prothalli first formed are not 
those which finally bear antheridia. 
The preceding remarks apply to sporangia attached to the leaf, the 
observations having been made on two plants of T. Fraseri growing in the 
Filmy Fern House at Kew 1 . In this species the production of antheridia 
inside sporangia attached to the leaf was observed in four different years, 
but was not seen on living plants of T. hymenophylloides , T. superba , Col. 
or T . Moorei , Baker. A few young prothalli were several times found in 
T \ hymenophylloides , and occasionally in the two other species, among the 
spores in closed sporangia, but these prothalli did not bear antheridia, and 
were usually not far enough advanced to do so. 
A short description of experiments may now be given. Pinnae or 
pinnules bearing dark green sporangia were removed from the living plant, 
and, while kept damp, were examined under a low power of the microscope, 
to see that none of the sporangia had burst 2 . The contents of some of the 
oldest sporangia were then examined, and, if germination had not begun in 
these, the other sporangia were taken as suitable for experiment. 
The essential feature in a number of the experiments consisted in 
keeping free spores and closed sporangia under similar conditions, and then 
comparing the mode of germination of the spores in the two cases. The 
free spores were taken from sporangia on the same leaf (usually on the 
1 At the time at which some of these observations were made, the temperature of this house 
was usually kept between io° and 13 0 C., but the best cases of intrasporangial germination were found 
in the warmer months, when the temperature was often considerably higher. 
2 When damp, sporangia, which have dehisced, may close again sufficiently to render close 
examination necessary. 
