402 Transactions. — Botany. 



Art. XXXVII. — On the Prothallium of Phylloglossum. 



By A. P. W. Thomas, M.A., F.L.S., Professor of Biology, 

 University College, Auckland.* 



Our knowledge of the development of the isosporous Lyco- 

 podincB is still so incomplete that no apology seems necessary 

 for the present preliminary statement. A special interest 

 attaches to Phylloglossum since it has been recognised as a 

 permanently embryonic form of lycopod.f Phylloglossum 

 is a genus with a single species — P. drummondii — confined to 

 Australia and New Zealand. The sporophyte generation is a 

 small plant growing from a tuber, which forms a tuft of a few 

 cylindrical tapering leaves. In fertile plants the apex of the 

 stem forms a peduncle, terminated by a cone or strobilus of 

 small scale-like fertile leaves. 



Treub has shown that the embryo of L. cernuum shows a 

 remarkable likeness to a barren plant of Phylloglossum, for the 

 first formed leaves have the character of the leaves of Phyllo- 

 glossum ; hence the term " protophylls " has been given to 

 these structures, so different from the ordinary leaves of 

 lycopods. Further, the embryo of L. cernuum forms at a 

 vfry early stage a tuber (protocorm), above which its proto- 

 phylls rise. To this protocorm the tuber of Phylloglossum is 

 apparently comparable, but in Phylloglossum it is not a passing 

 embryonic structure, but is repeated annually on the forma- 

 tion of a new protocorm. Treub regarded the protocorm as 

 the representative of a primitive structure originally possessed 

 by the pteridophytes, a structure which may have served an 

 important part in the phylogeny of the higher plants, in 

 enabling the sporophyte to attain an existence independent 

 of the gametophyte. 



The prothallia of Phylloglossum have been obtained growing 

 naturally amongst the parent plants, but it is a significant 

 fact that in most places, even where older plants are abundant 

 enough, no prothallia could be discovered, though many days 

 were spent in fruitless search. In three localities only were 

 prothallia discoverable. It appears clear that very special 

 conditions are necessary for the germination of the spores, 

 conditions which are not of regular annual occurrence wher- 

 ever Phylloglossum grows. Perhaps the most important of 

 these conditions is the presence of a fungus with which the 



* Reprinted fiorn the Proceedings of tho Royal Society, London, 

 vol. 69, p. 295, 5th December, 1901. 

 t Bower, Phil. Trans., 1886, p. 676. 



