34 Transactions. 



radicala displacing every other plant of excellent pastures in Nelson, are 

 without foundation. P. tenax has certainly been eradicated in many places, 

 and perhaps, in a sense, replaced by white clover, but not until fire and feed- 

 ing of stock had killed the plant. 



The great screes, called locally " shingle-slips/' which are such a 

 characteristic feature of mountain scenery in much of the South Island, 

 possess a most scanty and scattered vegetation, made up of some twenty-five 

 highly specialized species belonging to thirteen families, of which twenty 

 species occur in no other formation. Here the struggle between the indi- 

 viduals is nil, but that with the environment, especially the unstable sub- 

 stratum, is most severe. I know of no instance where a non-indigenous 

 plant has established itself on a true alpine shingle-slip.* In such a 

 station no plant could gain a footing unless provided beforehand with some 

 special " adaptations " fitting it for the severe conditions. The shingle- 

 slip association, moreover, is neither the climax of a succession nor is it part 

 of such ; it is an association complete in itself, and connected with no other. 

 Of a number of plants germinating by chance on a shingle-slip, the seedling 

 which possessed a slightly more xerophytic structure than its fellows would 

 be none the better, but would perish equally. Granting that natural selec- 

 tion can intensifyt characters by slow degrees, the conditions would select 

 too rigorously — there would be no survivors. It is almost equally diffi- 

 cult to see how epharmony could work, either. A plant to gain a shingle- 

 slip must come from some specially xerophytic station. This is shown 

 by the presence of Veronica epacridea Hook. f. and V. tetrasticha Hook, f., 

 rock-xerophytes. Perhaps the true shingle -slip plant Craspedia alpina 

 Backh., a summer-green herb with leaves in rosettes and thickly covered 

 with a deep snow-white wool, also arrived from some other formation, and 

 its abundant wool and deciduous leaves have arisen epharmonically. The 

 dimorphic succulent Claytonia australasica Hook. f. also occurs elsewhere, 

 one form being found in cold streams and damp gravel. Its rapid response 

 to a xerophytic stimulus accounts for its presence. 



The seedlings of the true shingle-slip plants are, so far as they have 

 been studied, strongly xerophytic at an early age. Thus an examination 

 of a seedling of Stellaria Roughii Hook. f. raised by me under mesophytic 

 conditions showed, " in the elastic stem, pale glaucous-green leaves, and 

 ■early succulence of the seedling, how hereditary are the most striking 

 peculiarities of shingle-slip plants" (Cockayne, 1901, pp. 267-69). 



An interesting point is the occurrence of two distinct species of 

 Cotula, or varieties of one species, it matters not, which are epharmonic- 

 ally equivalent. Taxonomically they differ in colour of florets, size of 

 flower-head, and size of involucre as compared with head. Accumula- 

 tive selection could do nothing here ; both plants thrive equally well, and 

 there is no competition except with the environment. Mutation alone 

 can explain this remarkable case, or some cause unknown. Another some- 

 what similar example is Notothlaspi rosulatum Hook. f. and N. australe 

 Hook. f. and its var. stellatum T. Kirk. Anisotome carnosula is in appear- 

 ance exactly like A. diver sifolia Cockayne, but there are technical differences 



* Introduced plants occur at times on small screes at base of rocks, and on river- 

 terrace scree in the lower mountain belt. 



f Weismann writes (191C, p. 01), "How often has the senseless objection being- 

 urged against selection that it can create nothing; it can only reject. . . . But in 

 rejecting one thing it preserves another, intensifies it, combines it, arid in this way 

 creates what was new." 



