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DISPERSION OF PLANTS IN YORKSHIRE: 

 NOTES ON ALIENS AND CASUALS RECENTLY 

 OBSERVED IN THE WAKEFIELD DISTRICT. 



By GEO. ROBERTS, 

 LoftJw7ise. near Wakefield \ Author of the ' Topography and Kat7iral History of 

 Lofthoiise and its Neighco?crhood.' 



There are now so many means of intercommunication between the 

 soutli of England and the north, and between the Continent and 

 the British Isles, that it is not surprising that Continental or south of 

 England plants should appear and become more or less established 

 in the northern counties in places where, half a century ago, they were 

 entirely unknown. In modern times Aliens have probably greatly 

 increased. Railways have greatly facihtated the diffusion of plants. 

 Seeds are constantly liable to be shaken from goods on railway trucks 

 during transit ; soil and rubbish, containing seeds or roots of perennial 

 plants, are often removed long distances along the railway as ballast ; 

 and the embankments and cuttings, being waste and seldom disturbed, 

 offer suitable locations for the growth and propagation of seeds or 

 roots thus scattered or removed. From the high banks the seeds 

 will be constantly blown, or by other agencies dispersed, to the 

 adjoining land. 



Another mode of introduction and dispersion is to be found in 

 the extensive and increasing importation of foreign agricultural seeds. 

 These foreign seeds — wheat, oats, barley, beans, grass, clover, flax, &c. — 

 all contain a greater or less quantity of seeds of weeds, which, when 

 sown, grow up with the ordinary crop. The distribution of weed- 

 seeds is further greatly facilitated by the present practice of thrashing 

 grain by steam machines in the fields. In this case the seeds are 

 blown and scattered in all directions over the land, whereas, formerly, 

 the refuse seeds were collected together and burnt, or otherwise 

 destroyed. Foreign Reeds, Bulrush {Scirpus Iacitst?'is), and other 

 plants containing dried seeds, are also introduced from the Continent 

 for thatching stacks and houses. Foreign hay is often imported, 

 which will contain quantities of the seeds of Continental grasses, 

 clovers and weeds. Various artificial manures — such as bone- 

 dust, mill-shoddy, cotton-waste, rape-cake, and guano — also con- 

 tain large quantities of exotic seeds. Numbers of roots of peren- 

 nial plants, bulbs, and seeds of weeds and garden plants are con- 

 tinually landed on canal-banks with the refuse of ash-pits, market 

 sweepings, timber, stone, and other merchandise. To these artificial 

 means of dispersion may be added the natural ones, as by the trans- 

 portation of seeds by rivers and smaller streams, by the winds, or by 



Dec. 1885. s 2 



