L. Cockayne and Foweraker. — Plant Associations at Cass. 173 



of rainy days is known for the Cass Biological Station a fairly accurate 

 measure will be afforded of the maximum toleration of rain by tussock 

 grassland. The description which loUows refers chiefly to the association 

 below 3,000 ft. altitude. 



The association is at the present time so greatly changed by burning 

 'and sheep-grazing that little idea can be formed of its primitive condition, 

 but it seems safe to coiiclude that the tussocks would generally touch and 

 that Discaria toumatou would be quite as abundant as at present, while Car- 

 michaelia subulata (so readily eaten by sheep), the now rather rare Aciphylla 

 sqimrrosa, and the grass Agropyron scahrum, then growing through the 

 tussocks, would be plentifid. On the other hand, the extremely abundant 

 small tussock, Poa Colensoi var., and a number of herbs and semi-woody 

 plants, now common, would be far less in evidence, especially Scleranthus 

 biflorus var., Coprosma Petriei (two varieties), and Senecio bellidioides (two 

 varieties or forms). 



Theoretically the dominant plant is the tussock Festuca novae-zealandiae, 

 but in reality Poa Colensoi var. is far more plentiful in many places, 

 while over considerable areas the Festuca is absent (see Plate XV, fig. 1). 

 The following, in addition to species already mentioned as abundant, 

 are common members of the association, the introduced plants being dis- 

 tinguished by an asterisk : Blechnum j)enna niarina (where shady), Lyco- 

 podiuin fastigiatum (where shady), *Holcus lanatus, *Poa pratensis, Carex 

 breviculmis, Luzula sp.. Microtis uniflora, Muehlenbeckia axillaris, *Rumex 

 Acetosella, Stellaria gracilenta, Scleranthus biflorus (two vars.), *Cerastium 

 triviale, Ranunculus multiscapus, Acaena Sanguisorbae var. pilosa, Geranium 

 sessiliflorum var. glabrum, Viola Gunninghamii, Pimelea prostrata var., 

 Epilobium elegans? Hydrocotyle novae-zelandiae var. montana, Gaultheria 

 depressa (where shady), Styphelia Fraseri (excessively abundant in many 

 places), Plantago spathulata, Wahlenbergia albomarginata, Celmisia longifolia 

 var., G. spectabilis (where shady), Brachycome Sinclairii, Raoulia suhsericea, 

 Gnaphalium Traversii, Cassinia fulvida var. montana, *Hypochaeris radicata 

 (many distinct forms apparently quite apart from change in environment). 

 At its higher levels the subalpine element becomes more abmidant, 

 Celmisia spectabilis being especially noticeable, while species confined to 

 shady stations at lower altitudes here grow in the full smishine. 



Where the association occurs on old flood-plain, and the ground is 

 stony, there is often an abundance of Carmichaelia uniflora, and here and 

 there open cushions of C. Monroi. In similar situations, forming a dis- 

 tinct subassociation, thanks to its twitch-like underground creeping stems, 

 the grass Triodia exigua forms a compact even turf. The pretty blue- 

 flowered Veronica pimeleoides var. minor is rather common in stony places, 

 and the easily overlooked Iphigenia novae-zealandiae is probably fairly 

 co mm on. The above lists by no means exhaust the florula of the associ- 

 ation, but they give a fair idea of its present composition for comparative 

 purposes with other parts of the formation in the South Island, and 

 prepare the way for the necessary detailed and experimenal study that 

 should next follow. 



Although not all the introduced plants are mentioned, it can be seen that 

 they are far from numerous ; in fact, they play comparatively little part 

 as yet in the economy of the association. Nor is it to be expected that 

 they will greatly increase either in number or aggressiveness under the 

 present condition of affairs. The truth seems to be that a balance has 

 been reached and that a plant association unknown in primitive New 

 Zealand is now well established. 



