TEANSACTIONS OF SECTION D. 199 



parently (though I am not certain on the point) self-fertiHsable, 

 while under favourable conditions of fine weather and sunlight 

 it is visited by many species of insects. Alongside of this plant, 

 the common European dandelion — Taraxacum dens-leonis, 

 half-brother to the indigenous form — has been introduced under 

 apparently similar conditions ; yet it has never become as widely 

 spread, being confined, as in Britain, to roadsides and waste 

 places. There is no doubt that it is a more highly specialised 

 form in many respects than Hypoclioeris, but to the popular eye 

 this fact is not patent. I instance these two familiar weeds 

 as showing how very difficult it is, at first sight, to assign 

 causes for success or failure in naturalisation. Other instances 

 of remarkable developement among introduced plants are the 

 spread of watercress in the streams on the Canterbury plains, 

 where, however, I am inclined to think that the gigantic de- 

 velopment of the first few years is followed by a gradual return 

 to a more normal rate of growth* ; the rapid spread of sorrel 

 {Bumex acetosella) and Poa lyratensis as weeds of cultivation, 

 and numerous others. 



The use of straw, hay, &c., as bedding and packing material 

 has brought great numbers of plants into the country. I have 

 found various European plants, not found elsewhere in the dis- 

 trict, growing near seaports where immigrants' chaff-bedding 

 used to be landed, and in part burned ; and it has often struck 

 me as a curious fact how limited the distribution of such plants 

 is, and how slowly they spread. Thus, at Port Chalmers, 

 Veronica buxbaumii occurs, but I have not observed it else- 

 where in the east part of Otago. Again, Sherardia arvensis 

 and Fumaria caprcolata, var. mural is, have been common for 

 many years in one part of the suburbs of Duuedin, but I have 

 not observed them to extend their range. The same remark 

 applies to Galium aparine, a plant apparently well fitted for 

 distribution on account of its adhesive fruit. Again, I have 

 watched Bartsia viscosa spreading slowly north and east from 

 a point near Abbotsford, in the Green Island district, and in 

 the last nineteen years it has not extended more than six or 

 eight miles, while in the opposite direction (against the pre- 

 vailing winds) it does not seem to have spread at all. 



Many species of insects (and a few molluscs, &c.) have been 

 introduced in the same accidental manner, and in some 

 instances have become readily naturalised. Many of these, 

 like Aphides, some Coccidae, &c., have been brought into the 



* In this respect the thistle is remarkable. Newly-ploughed land, 

 e.g., in North Otago, is invaded by this plant to such an extent that it 

 becomes an impassable thicket ; but this condition does not last more 

 than two or three years, after which the land is found to be unable 

 again to produce such a dense growth of the weed, while its fertility is 

 improved by the accumulation of vegetable mould. 



