3 Holloway. — The Protlvallus and Young Plant of Tmesipteris. 



Occurrence and Habit. 



Tmesipteris occurs commonly throughout New Zealand as an epiphyte 

 on the stems of tree-ferns and other forest-trees. The much-branched 

 brown rhizome penetrates through the mass of aerial rootlets which densely 

 clothes the stem of the tree-fern, and especially is to be found under- 

 neath the decurrent stipites of its fronds. Certain of the rhizome- 

 branches turn upwards, and emerge as green aerial shoots, bearing 

 scattered scale leaves below and above the full-sized leaves of charac- 

 teristic form and the sporophylls. 



There is a certain amount of variation noticeable in the habit and 

 general form of the plant, which is probably to be put in connection with 

 the nature of the surface on which it grows. However, it must be noted 

 that some writers have recognized distinct varieties. For example, when 

 growing on certain species of the tree-fern Cyathea the whole plant is gene- 

 rally somewhat stunted in size, the rhizome being more scantily branched 

 and the aerial shoots short and semi-erect. In these cases the surface of 

 the tree-fern stem consists solely of the mat of black brittle aerial rootlets, 

 the stipites of the fronds not reaching down the stem much below its 

 crown, and consequently there being only the dense tough mat, of greater 

 or lesser thickness, of the interlaced rootlets in which the Tmesipteris 

 plants can grow. My experience has been the same probably as that of 

 others who have tried to dissect out the plants from such intractable 

 material. It is almost impossible to get the plant with all its various 

 branchlets complete, and one gives up in despair the search for the young 

 plants or for the prothallus. 



In those parts of New Zealand, however, especially in the botanical 

 districts, as defined by L. Cockayne,* which lie for the most part west of 

 the Southern Alps, together with that ecologist's South Otago and Stewart 

 Districts, where the average rainfall is very heavy, there is an extremely 

 rich growth of Pteridophytes, and Tmesipteris occurs abundantly on the 

 tree-fern Dicksonia squarrosa and on moss- or humus-covered forest-trees, 

 and also in the heaps of humus which lie on the ground at the bases of the 

 trees. Here the size and habit of the plant are markedly different from those 

 described above. The penetrating rhizomes may be as much as 2 ft. or 

 3 ft., or even more, in total length, and are for the most part extensively 

 branched ; also, it is an easier matter to dissect out a plant entire from 

 such a substratum. The aerial branches arising from a single plant are 

 fairly numerous, and droop down 2 ft., 3 ft., and 4 ft. in length, the branches 

 of groups of plants hanging like a fringe from some tree-branch or fallen 

 tree-stem. In Plate I is shown a single plant with a much-branched 

 rhizome and three aerial stems, the latter showing fertile regions. 



I have found in the neighbourhood of Hokitika, Westland, in the low- 

 lying forest which borders the sea-front, both young and mature plants 

 of Tmesipteris growing on the stems of Dicksonia squarrosa in great 

 abundance. On this particular tree-fern the frond-stipites run down the 

 stem for some distance before they enter its surface, and hence in young 

 individuals the greater part of the stem, and in older plants the upper 

 portion, is covered with the adhering bases of the fronds. The young 

 plants of Tmesipteris occur both immediately underlying the stipites and 

 in the ridges of aerial rootlets which project outwards between them. 

 During the month of September, 1917, I obtained several lengths of tree- 



* Trans. N.Z. Inst., vcl. 49, p. 65, 1917. 

 1* 



