358 Trax^action.^. 



(h.) Sliiagle-slip. 

 * General. 



The edaphic distinction between shingle-slip and fell-field lies in the 

 fact that the former consists altogether of loose stones lying at so steep a 

 slope that those of the uppermost layer move downwards from time to time, 

 whereas the stones of the fell-field are in a much more stable position, and 

 there is generally a considerable percentage of true soil. This instability of 

 shingle-slip has led to the occupation of this land-form not merely by cer- 

 tain growth-forms, but actually by distinct species which do not occur in 

 any other formation. Fixrthermore, the plants are distant so far from one 

 another, and the general plant covering is so scanty, that it plays no part 

 worth mentioning in adding humus to the soil, while the formation is dis- 

 tinct in itself and has nothing to do with the installation of fell-field. It is, 

 in fact, a definite vegetation entity whose life-history it is now impossible 

 to examine, and whose origin is wrapped in obscurity. 



The shingle-slip species are confined to the South Island, | and the 

 majority to the drier mountains of the east. The following is a list of those 

 found in the Arrowsmith district in its widest sense : Stellaria Roughii 

 (Caryophyll.) ; Eanunculus Haastii, R. crithmijolius, R. chordorhizos (Ranunc.) ; 

 Notothlaspi rosulatum (Crucif.) ; Acaena glabra (Rosac.) ; Swainsona novae- 

 zealandiae (Legum.) ; Epilobium fycnostachyum (Onagrac.) ; Anisotome carno- 

 sula (Umbell.) ; Myosotis Traversii (Borag.) ; Lobelia Roughii (Campan.) ; 

 Veronica Haastii (Scrophular.) ; Haastia Sinclairii, Crasfedia alfina, Cotula 

 at rata (Compos.). 



The following are also frequent members, but are not confined to shingle- 

 slip : Claytofiia australasica (Portulac), Anisotome filifolia (Umhell.), 

 Veronica tetrasticha, V. lycofodioides, V. epacridea (Scrophular.). 



** Groivth-fonns. 



The shingle-slip plants afford a most admirable example of convergent 

 epharmony. Nearly all are summer-green low-growing or prostrate herbs, 

 with the leaves more or less in rosettes, though these are frequently masked 

 through the stems, which have the power of lengthening as buried, being 

 covered with debris. The leaves of almost all are fleshy or coriaceous, 

 glabrous, glaucous, and almost the colour of the stones, and in some cases 

 very deeply divided, the bending-together of the final segments much 

 reducing the leaf-surface. Haastia Sinclairii and Craspedia alpina are 

 densely woolly, the latter, clothed with long snow-white wool, being especi- 

 ally noticeable. The species of Ranunculus and Anisotome carnosula have 

 stout fleshy rhizomes ; Lobelia Roughii and Swainsona slender but far- 

 spreading much-branching stems creeping amongst the stones. Notothlaspi 

 rosulatum is annual or biennial. 



The texture of leaves and stems is such as to withstand the blows of 

 sliding stones, and the plants as a whole can grow upwards, as buried, after 

 the manner somewhat of dune-plants, though, of course, to a much lesser 



degree. 



*** Ecological Coyirtltionf:. 



t Eda))liic'. 

 The soil consists of loose angular fragments of stone, frequently quite 

 small, lying upon one another, and the slope of the surface is so steep that 



X Veronica spathulata of scoria slopes in the central volcanic plateau lias a shinglc- 

 slip form. 



