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Prothcdli in Sporangia of Todea . 
When a considerable number of spores germinate in the sporangium, 
some of the prothalli (apparently not those first formed) produce antheridia. 
Usually a single antheridium is borne terminally on a prothallus of only 
three or four cells (occasionally of one or two cells), and in these specimens 
the rhizoid is generally not developed. 
Sporangia, whether detached, or attached to a pinnule or pinna, behave 
similarly to those attached to the living plant. If kept sufficiently damp to 
prevent dehiscence (and with other conditions favourable), intrasporangial 
germination takes place, and prothalli bearing antheridia are ultimately 
formed. Antheridia were found in one experiment after twenty-one days. 
The prothalli do not appear to be capable of bursting the wall of the 
sporangium, and ultimately die. Motile spermatozoids were not seen, but 
once or twice the bursting of the antheridium and the emission of the 
sperm-cells were observed. 
Free spores, placed under the same conditions as the sporangia, never 
produced dwarf male prothalli, but formed normal prothalli, which had not 
developed sexual organs at the conclusion of the experiments. 
Free spores germinate in the dark in tap-water at the temperature of 
the experiments (roughly between 1 6 ° and 2i° C.), and the prothallus may 
at any rate reach a six- or seven-celled stage. Spores also germinate in 
the closed sporangium in the dark, and under favourable conditions dwarf 
prothalli with antheridia are produced. 
In Todea hymenophylloides the spores germinate less readily than in 
T. Fraseri. This may be due to the smaller amount of oil present in the 
spores of the former species. In T. hymenophylloides prothalli bearing 
antheridia were found in closed sporangia in only one or two experiments ; 
they were not seen in sporangia on the living plant, though germination of 
a few spores was observed several times. As in T. Fraseri , free spores 
always produced normal prothalli. In T. Moorei and T. superb a slight 
germination of spores in the sporangium was observed, but these species 
were not used in experiments. 
A possible explanation of the formation of dwarf male prothalli in the 
sporangium is suggested. The mechanical hindrance to the growth of the 
prothalli caused by the pressure of the wall of the sporangium probably 
causes concentration of certain organic food substances. This may lead to 
special nutrition of the protoplasm, and this again may cause the pre- 
cocious formation of sexual organs. Scarcity of water in the sporangium 
may perhaps have a similar influence. 
Literature referred to. 
Atkinson (’94) : The Study of the Biology of Ferns by the Collodion Method, New York. 
Beck (’ 78 ) : Entwickelungsgeschichte des Prothalliums von Seolopendrium vulgar e. Bot. Zeitung, 
Jahrg. 3 6, p. 780. 
