238 Transactions. 



young plant is very peculiar. Any similarities in detailed structure between 

 this type and any of the others are perhaps best regarded as instances of 

 parallel development, such as the fungal " palisade " tissue in the prothallus 

 of L. cernuum and of L. clavatum and L. cotnplanatum, and also the elongated 

 manner of growth in L. ramulosum and L. Billardieri. The varieties in 

 form and structure which occur in the prothalli of the cernmim type are 

 chiefly interesting as evidences of the great plasticity of the Lycopodium 

 gametophyte. It is in the Cernua and Inundata sections that we meet 

 with the least evidence of a permanently fixed type of prothallus. These 

 prothalli have also proceeded the least of all to a saprophytic mode of 

 life, and generally show the least extent of specialization. The epiphytic 

 prothalli have become thoroughly specialized to the epiphytic habit, and 

 the clavatum and complanatum types, to the subterranean terrestrial habit. 

 We are justified, therefore, in regarding the Cernua and Inundata types 

 as showing more nearly the original structure plan of the Lycopodium 

 prothallus than the others. 



Thus we may ^conclude from a comparative study of the general form 

 and structure of the different Lycopodium prothalli that they are all more 

 or less modified from some primitive type of structure, and that the chief 

 factor in this modification has been the presence in them of the symbiotic 

 fungus. This, primitive type of structure was probably a more or less 

 bulky filament of radial build, situated at the surface of the ground, and 

 possessing chlorophyll. The adoption of a fungal habit opened the door 

 to possibilities of modification of this simple type of structure, and gave 

 to the Lycopodium prothallus its quality of plasticity. It was able to 

 establish itself in new positions and soils, the different types of habitat 

 resulting in different types of modification of the original structure. When 

 the fungal habit was thoroughly adopted the early filamentous stage became 

 lost, but in all its forms the Lycopodium prothallus has never departed 

 from the radial build. 



It seems clear from a comparative survey of all the main characters 

 of the Lycopodium sporophyte and gametophyte that the different sections' 

 of the genus are natural ones, and that their characters are all inter- 

 dependent. It is possible that the varied aspect of the genus as it exists 

 to-day has been due largely to the phenomenon of symbiotic association 

 with a fungus exhibited by its gametophyte generation, the varied structure 

 of the sporophyte as regards the form adopted by the mature plant, the 

 form of its spore-bearing regions, and its stem-anatomy following as a 

 natural consequence from the spread of the gametophyte to different stations 

 and soils. 



Literature cited, ' 



1. Bbuchmann, H., Jlber die Prothallien und die Keimpflanzen mehrerer europdischer 



Lycopodien, pp. 1-119, pi. 1-8, Gotha, 1898. 



2. Die Keimung der Si3oren und die Entwickelung der Prothallien von Lyco- 

 podium clavatum, L. annotinum, und L. Selago, Flora, vol. 101, pp. 220-67 

 (35 figs.), 1910. 



3. Chamberlain, C. J., Prothallia and Sporelings of Three New Zealand Species of 



Lycopodium, Bot. Gaz., vol. 63, pp. 51-64, pi. 2 and 3, 1917. 



4. Edgerley, Miss K. V., The Prothallia of Three New Zealand Lycopods, Trans. 



N.Z. /rw<., vol. 47, pp. 94-111 (37 figs.), 1915. 



5. GoEBEL, K., ijber Prothallien und Keimpflanzen von Lycopodium Inundatum, 



Bot. Zeit., vol. 45, pp. 161-68, pi. 2, 1887. 



6. Hollow AY, J. E., A Comparative Study of the Anatomy of Six New Zealand 



Species of Lycopodium, Trans. N.Z. Inst., vol. 42, pp. 356-70, pi. 31-34, 1910. 



7. Studies in the New Zealand Species of the Genus Lycopodium, Part I, Trans. 



N.Z. Inst., vol. 48, pp. 253-303 (102 figs., pi. 17, 18), 1916. 



