T. KiKK. — Oil the Products of a Ballast-heaj). 501 



Art. XLIX. — On the Products of a Ballast-heap. 

 By T. KiiiK, F.L.S. 



[Read before the Wellingto7i Philosophical Society, 26th February, 



1896.] 



During the summer and autumn of 1892 and 1893 attention 

 was drawn to the introduction of injurious weeds in earth - 

 ballast, as exemplified by the introduction of the cockle-burr''' 

 (Xanthium strumarium, L.), in the ballast of the ship " Silver- 

 stream " from Buenos Ayres, which had been temporarily 

 deposited near the Bunny Street entrance to the railway 

 goods-station, Wellington. As the total number of species 

 exceeded one hundred, and 20 per cent, of them were new to 

 the colony, it seems advisable to record this short chapter in 

 the history of the introduction of exotic plants in New Zea- 

 land at some length, more especially as the great majority of 

 the newcomers are of South American origin, and hitherto less 

 than a dozen of our naturalised plants have come from that 

 part of the globe. 



The ballast, of which some portion had been removed 

 when I first saw it, originally covered an area of about 40ft. 

 in breadth by 70ft. or 80ft. in length, with a general height 

 of 3ft. or -Ift. It had been clothed with a dense weedy 

 growth, which had been cut down by the railway authorities, 

 who learned the possibility of some of the plants proving 

 noxious from the newspapers of the day. The ballast itself 

 consisted chiefly of soil from cultivated land sparingly mixed 

 with fragments of brick and other building rubbish. Portions 

 of the earth were distributed some yards beyond the original 

 area during its removal for the formation of a new platform at 

 the passenger-station, so that certain of the plants were 

 scattered for some distance along the line of removal. 

 Although the soil was removed so closely that the old surface 

 was laid bare in most places, numerous seed-containing par- 

 ticles were left behind, when several plants which had not 

 been previously observed made their appearance for the first 

 time. 



The total number of plants collected is 101, of which 

 about seventy belong to the great army of combatant weeds 

 which have now become distributed along the great lines of 

 ocean-travel all round the earth, and for the most part appear 

 to find little difficulty in establishing themselves and encroach- 

 ing upon their iuiligenous congeners when once introduced : 



* See Trans. N.Z. lust., xxvi. (1893), 310. 



