Hollo way. — Prothallus, &c, of Tmesipteris. 387 



General. 



The climate of Westland is a continuously wet one, there being practically 

 no really dry periods at any season of the year. For example, at Hokitika, 

 on the coast, as shown in the Meteorological Office records, for the ten years 

 1909 to 1918 the average annual rainfall was 117-36 in., the lowest for any 

 one year being 100-97 in. and the highest 134-32 in. A detailed examination 

 of these records shows that during this decade twice only was the monthly 

 rainfall less than 2 in., while generally speaking the annual total was fairly 

 evenly distributed over the twelve months, and no one month in the year 

 showed usually a markedly less rainfall than any other. As a general rule, 

 also, the Westland climate is characterized by the absence of dry winds. 

 On the main mountain-ranges, which run more or less parallel with the coast, 

 the rainfall is, of course, much heavier than at sea-level, this being especially 

 so in the gorges and on the lower flanks of the ranges. For example, at 

 Otira, at the western end of the tunnel which pierces the main divide, on the 

 Midland Kailway, lying at an altitude of 1,255 ft., the average rainfall for 

 the five years 1914 to 1918 was 198-73 in. 



On account of the wet climate and constantly high humidity the whole 

 district from sea-coast to the mountain-ranges is covered with heavy forest, 

 and the growth of ferns and other cryptogamic plants is luxuriant both 

 epiphytically and on the floor. Tree-ferns, especially Dicksonia squarrosa, 

 are abundant in the lowland forest and up to the bases of the mountains. 

 Away from the coast Metrosideros lucida (the southern rata) is a common 

 member of the forest, and its large much-branched and irregularly-growing 

 trunks frequently show thick accumulations of epiphytic humus with 

 colonies of Pteridophytes. 



In the coastal forest Tmesipteris occurs abundantly on the steins of 

 Dicksonia, being frequently accompanied in this station by Lycopodium 

 Billardieri var. gracile and by the two filmy ferns Hymenophyllum Jerru- 

 gineum and Trichomanes venosum. In this part of the district the mature 

 plants of Tmesipteris also occur, but far less frequently, in the forks of large 

 trees or even on the ground. Colonies of young plants can often be found 

 on the tree-fern stems, the youngest plants being invariably at the upper- 

 most limit of the colony. The most favourable place for the germination of 

 the spores is clearly that part of the stem in which the bases of the frond- 

 stipites are beginning to form a firm but not too dense substratum with an 

 accumulating humus by the extension upwards of the tree-fern's clothing 

 of aerial rootlets. As the Dicksonia grows in height the Tmesipteris plantlets 

 extend upwards, those farther down the stem exhibiting progressively older 

 stages of development. These are favourable places for finding prothalli, 

 in some cases in relative abundance. I have dissected out from selected 

 portions of tree-fern steins a total of considerably over one hundred 

 prothalli. In this coastal forest, and even farther inland wherever Dicksonia 

 occurs commonly, one can always be sure of obtaining the young plants and 

 prothalli, although the work of dissecting them out from the tree-fern-stem 

 surface is generally tedious and requires considerable care. Undoubtedly 

 the easiest places in which to find the prothalli of Tmesipteris are the large 

 overhanging trunks of the rata, where, as has been mentioned previously, 

 humus frequently accumulates to a considerable depth on the upper sides 

 of the trunks and lower limbs and in the crevices, within easy reach of the 

 ground. Here colonies of large mature plants are to be met with, the humus 

 being permeated with their rhizomes. The young plants, if present, occur 

 quite indiscriminately, there being an absence of the useful grading which is 



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