NOTES ON RECENT RESEARCH. 



703 



at sea-level. Their thick fleshy rhizomes are tunnelled by a system of 

 galleries, similar to those of Myrmecodia and Hydnophytum, and which 

 are, like them, invariably inhabited by colonies of ants. " In both Ferns 

 a tissue consisting of large cells with thin walls and no intercellular 

 spaces is formed in certain definite areas near the apex of the stem. 

 This tissue breaks down at an early period, its place being taken by the 

 ant-galleries, which are thus of lysigenous origin. The gallery system 

 consists in both cases of a main ventral gallery which runs longitudinally 

 through the stem, giving off two lateral series to the branches and two 

 series of vertical ones leading to the swollen leaf-cushions. Soon after 

 leaving the main gallery the vertical ones branch so as to form two 

 longitudinal series of dorsal chambers." Differences between the two 

 species, with regard to these chambers, are then described. Continuing, 

 the author says that " communication between the galleries and the 

 external air is effected by means of short passages excavated by the ants 

 themselves in the soft tissues of the younger parts of the stem. The 

 character and topographical position of the large-celled tissue seem to 

 indicate that it was developed in the first instance as a special water 

 reservoir ; but the fact that it is soon disintegrated may perhaps point to 

 some degree of change of function, i.e. that the galleries which replace 

 it have some important function to fulfil. There is no evidence that the 

 galleries are an adaptation on behalf of the ants, and indeed their mean- 

 ing is still somewhat obscure. Perhaps they serve as organs for the 

 aeration of the stem, which is in both cases almost devoid of intercellular 

 spaces. It is also possible that they assist to a slight extent in the 

 absorption of water." The species of ant is not the same in both species 

 of Polypodium, P. sinuosum being inhabited by Technomyrmex albipes, 

 and P. carnosum by a new species of Cremastogaster, C. Yappi of Forel. 

 Although the possibility of the existence of a true adaptation between 

 the ants and the Ferns cannot be denied, yet available evidence, the 

 author says, seems to point to Goebel's view as being the correct one, 

 i.e. that the ants are merely " Raumparasiten," or dwellers in cavities 

 formed without reference to their future inhabitants, more particularly so 

 because no attraction in the form of food appears to be offered to the 

 ants. Pteridologists are indebted to the author for his careful examina- 

 tion of these Ferns, especially in the case of P. carnosum, the position 

 of which has been debatable. Reinwardt originally placed it in the 

 genus Onychium, while a few years later Blume described it as the type 

 of a new genus with the name Lecanopteris. The majority of writers 

 have maintained this genus, and in 1892 Baker wrote, " I now think that 

 Lecanopteris will have to stand as a distinct genus in the neighbourhood 

 of Dicksonia, from which it differs in having an indusium formed of only 

 a single valve and in the curious rootstock." The author shows, how- 

 ever, that the supposed indusium is in reality part of the ordinary leaf- 

 lamina, and, resting on this, it is easy to agree with him in his 

 determination. He says that " the only reason that remains for 

 retaining Lecanopteris as a distinct genus is the curious reflexed position 

 of the sori." The sorus-cups are brought to face skywards, and what 

 this means in the economy of the plant is of much interest. The plants 

 grow on the upper branches of trees, in one locality never at less than 



