Holloway. — The Prothallus and Young Plant of Tmesipteris. 5 



large globular cushions of mosses and liverworts {e.g., Dicranoloma Bil- 

 lardieri and species of Plagiochila) from 1 ft. to 2 ft. or more in diameter, 

 and with three species of Lycopodium (L. volubile, L. scariosum, and L. 

 varium) growing in wonderful luxuriance. Lycopodium varium here grows 

 in great clumps, which are as much as 6-8 ft. across. Tmesipteris and 

 filmy ferns are also in great abundance — in fact, the general appearance 

 of the vegetation is suggestive of a past age when Gymnosperms and 

 Pteridophytes were dominant rather than Phanerogams. During my visit 

 to Stewart Island I arranged an expedition to spend a few days in this 

 locality, but owing to heavy rains and floods the party was isolated on 

 the sea-coast and nearly met with disaster. However, on the last day 

 I reached the spot, and during an hour's search succeeded in finding 

 several young prothallial plantlets of Tmesipteris growing in thick loose 

 humus on a fallen tree-trunk. There is no doubt that with longer time 

 at his disposal a searcher would find the place a most favourable one for 

 the discovery of both the young plants and the prothalli. 



It was not till the spring of 1917 that the further discovery was made, 

 in the neighbourhood of Hokitika, of both plantlets and prothalli of 

 Tmesipteris, as recorded above. In the dissection of these specimens 

 from the mass of aerial rootlets on the stems of the tree-ferns a certain 

 amount of patience and care had to be used, for these rootlets are ex- 

 ceedingly tough and are closely intermatted, and both the prothalli and 

 rhizomes of Tmesipteris are very brittle and easily broken. However, 

 by pulling away the stipites of the tree-fern fronds and carefully tearing 

 apart the mass of aerial rootlets the golden-yellow rhizomes and the brown 

 prothalli were easily to be seen (by reason both of their characteristic 

 colour and of their comparatively large size), and, the black aerial rootlets 

 being cut away with dissecting scissors, they were readily obtained. 



General Form and Structure of the Prothallus. 



The prothallus-body is cylindrical in form, being radially constructed. 

 It is brown in colour, and is covered with numerous long golden-yellow 

 rhizoids. It never seems to reach the light, and is quite destitute of 

 chlorophyll. The largest specimens found are shown in figs. 5, 6, and 8, 

 being 18 mm. and 13 mm. respectively in total length, and the smallest 

 in figs. 11 and 12, these being from 1 mm. to 2 mm. long. In its un- 

 branched form the prothallus is carrot-shaped, tapering down gradually 

 from a fairly thick head and upper region towards the basal first-formed 

 end, which culminates in a more or less long-drawn-out point (figs. 1, 2, 

 and 11). The first-formed basal region does not show such a marked 

 primary tubercle as is so well known in the case of the prothalli of 

 Lycopodium cernuum or in those of Ophioglossum and Helminthostachys, 

 but there is commonly a succession of gentle swellings from the original 

 point of growth upwards by which the prothallus grows in girth (figs. 1, 2, 

 11, and 13). The actual head is generally the stoutest region (figs. 12, 

 13, &c), being sometimes curiously swollen, and the growing apex is 

 bluntly rounded. 



Sooner or later the head of the prothallus forks dichotomously, and 

 one of the branches so formed may later fork again. In some cases the 

 first branching is postponed till after the prothallus has attained a length 

 of as much as 8-10 mm. (figs. 1, 2), and the result is the carrot form ; 

 more often, however, the first forking takes place comparatively early 

 (fig. 6), and many adult prothalli were found in which one of these 



