chap, xxiii.] ARCTIC PLANTS IN NEW ZEALAND. 
483 
general conditions being more favourable, it was able to 
establish itself as a permanent member of the flora. Such, 
generally speaking, was probably the process by which the 
Scandinavian flora has made its way to the southern hemi- 
sphere ; but it could hardly have done so to any important 
railway from Yarmouth to Caistor in Norfolk, where it passes over exten- 
sive sandy Denes with a sparse vegetation. The first year after the 
railway was made the banks produced abundance of (Enotliera odorata 
and Delphinium Ajacis (the latter only known thirty miles olf in corn- 
fields in Cambridgeshire), with A triplex patula and A. deltoidea. Gradually 
the native sand plants — Carices, Grasses, Galium vcrum, &c., established 
themselves, and year by year covered more ground till the new introduc- 
tions almost completely disappeared. The same phenomenon was observed 
in Cambridgeshire between Chesterton and Newmarket, where, the soil 
being different, Stellaria media and other annuals appeared in large patches ; 
but these soon gave way to a permanent vegetation of grasses, composites, 
&c., so that in the third year no Stellaria was to be seen. 
5. Mr. T. Kirk (writing in 1878) states that — “ in Auckland, where a 
dense sward of grass is soon formed, single specimens of the European Milk 
Thistle ( Carduus marianus) have been known for the past fifteen years ; 
but although they seeded freely, the seeds had no opportunity of germinat- 
ing, so that the thistle did not spread. A remarkable exception to this 
rule occurred during the formation of the Onehunga railway, where a few 
seeds fell on disturbed soil, grew up and flowered. The railway works 
being suspended, the plant increased rapidly, and spread wherever it could 
find disturbed soil.” 
Again: — “The fiddle-dock ( Rumex pulcher ) occurs in great abundance 
on the formation of new streets, &c., but soon becomes comparatively rare. 
It seems probable that it was one of the earliest plants naturalised here, 
but that it partially died out, its buried seeds retaining their vitality.” 
Medicago sativa and Apium graveolens, are also noted as escapes from 
cultivation which maintain themselves for a time but soon die out. * 1 
The preceding examples of the temporary establishment of plants on 
newly exposed soil, often at considerable distances from the localities they 
usually inhabit, might, no doubt, by further inquiry be greatly multiplied ; 
but, unfortunately, the phenomenon has received little attention, and is 
not even referred to in the elaborate work of De Candolle ( Geographic 
Botanique Raisonnee ) in which almost every other aspect of the dispersion 
and distribution of plants is fully discussed. Enough has been advanced, 
however, to show that it is of constant occurrence, and from the point of 
view here advocated it becomes of great importance in explaining the 
almost world-wide distribution of many common plants of the north 
temperate zone. 
1 Transactions of the New Zealand Institute, Vol. X. p. 367. 
I I 2 
