On the Production of Dwarf Male Prothalli in 
Sporangia of Todea. 1 
BY 
L. A. BOODLE, F.L.S., 
Assistant , Royal Botanic Gardens , Kew. 
With Plate XVI. 
W HEN examining sporangia of filmy species 2 of Todea , a few years 
ago, I was surprised to find that closed sporangia attached to the 
leaf sometimes contained antheridia, owing to the spores having germinated 
and at once formed the male organs. This appeared so interesting that 
I attempted by a series of experiments (in 1904 and 1905) to gain some 
light on the cause of this precocious formation of sexual organs. Such 
results as were obtained did not lead very far towards an explanation of 
the phenomenon, though determining its relation to certain conditions. 
Publication 3 was consequently postponed awaiting an opportunity of making 
further experiments. As, however, the phenomenon itself is of some 
importance, it seems advisable not to delay longer, but to place the 
observation on record with the results obtained, in the hope that other 
botanists may carry the matter further. 
Todea Fraseri, Hook, et Grev. and T. hymenophylloides , Rich, et Less, 
were the species on which most of the observations were made, and, of 
these, T. Fraseri was found to be more ready to form intrasporangial 
antheridia. The mature sporangia are dark green owing to the dense 
chlorophyllous contents of the ripe spores, and ultimately appear greenish 
black by reflected light. It is in these very dark sporangia after they have 
passed maturity that antheridia are sometimes to be found. An example 
is given in PI. XVI, Fig. 1, which is from a microtome-section of a closed 4 
sporangium obtained from a fertile leaf of T. Fraseri. The spores are 
seen to have germinated and produced antheridia, eight of which are visible 
in this section. The details are better seen in Fig. 2, which represents the 
1 From the Jodrell Laboratory, Royal Botanic Gardens, Kew. 
2 The filmy species of Todea , Willd. (cf. Synopsis Filicnm) form the genus Leptopteris of Presl. 
3 A short preliminary account was read before Section K of the British Association at Cambridge 
in 1904. 
4 The injuries in the wall of the sporangium are due to the dragging of the razor. 
[Annals of Botany, Vol. XXII. No. LXXXVI. April, 1908.] 
