320 Transactions. — Botany. 



and to assume a more normal rate of individual develop- 

 ment. It is as if the restrictions which formerly kept it 

 withiu certain limits had been removed, and it sprang with 

 a bound to a height of vigour which it was not able to 

 maintain, and then had gradually fallen back to a level at 

 which it could maintain itself. Anglers recall the marvellous- 

 rapidity with which trout grew when they were first put 

 into our streams. The food-supply was practically unlimited,, 

 and they increased most remarkably m size and weight. 

 But succeeding generations have not been able to keep up 

 the same phenomenal rate of growth, for not only is the 

 food-supply diminished, but the young fish have to run the 

 gauntlet of the old ones, which are their worst enemies. 

 This factor does not, of course, enter to anything like the 

 same extent into the relations of plants to one another, but 

 it is to be taken into account in considering that well- 

 established plants are most formidable rivals to the seed- 

 lings of their own kind round about them. A somewhat 

 analogous case seems to be that of the humble-bees. 

 During the first few years after their liberation in Canter- 

 bury these insects increased enormously in numbers, and 

 bee-keepers frequently expressed the opinion that they would 

 soon crowd the hive-bee out of existence. But, as far as I 

 can make out, this rate of increase has not been maintained, 

 and these insects are now by no means troublesome on 

 account of their numbers. 



The same phenomenon has been witnessed in the case 

 of some plants. The marvellous growth of w r atercress in 

 the streams of the Canterbury Plains, producing as it did 

 stems of 12 ft. in length and fin. in diameter, has often been 

 adduced. But I do not think that this huge type of growth 

 has been kept up to any extent, though I am open to cor- 

 rection on this point. As far as I have seen it about Christ- 

 church, the plant seems to grow larger than the parent 

 plants in Britain, but it does not attain its former recorded 

 dimensions. 



When the Oamaru district was first ploughed the common 

 thistle (Cardutcs lanceolatus) took absolute possession of the 

 soil. I remember walking in 1872 through many hundreds of 

 acres on the Balruddery and Elderslie properties, between the 

 Waiareka and Kakanui Rivers, and the only available track 

 was on the dray-ruts, and even there the thistles were waist- 

 deep, while on both sides they formed a wall 6 ft. or 7ft. high. 

 During the first year or two of their occupation not a blade 

 of grass or other plant could show itself, but afterwards the 

 ground seemed to become somewhat sick of thistles. Mean- 

 while the soil was enriched by the plentiful supply of vege- 

 table matter which was produced on it and ultimately 



