390 ROBERTS: YORKSHIRE ALIEN AND CASUAL PLANTS. 



birds and other animals, and on floating caddis cases. Thus, as some 

 of our native plants become extinct, others appear which help to main- 

 tain, if not augment, the aggregate of our flora. Indeed, this gradual 

 replacement of one flora by another, of annuals by perennials, is con- 

 stantly (if slowly acting) going on, not only on railway banks and near 

 our towns, but in the far away rural districts, the higher and moor- 

 lands alone excepted. 



The following plants, a number of which are Aliens, have been 

 collected or observed mainly in the Wakefield District during the years 

 1883-4-5. The rarer species, I may add (both exotics and British), 

 have been either named by Dr. Lees, or sent to the Royal Botanic 

 Gardens for verification. 



The exotic Aliens are marked by a double asterisk ; the single 

 asterisk is prefixed to Casuals which have not hitherto been frequently 

 found so far north as Yorkshire, but which are constant integers in 

 the flora of the south or south-west of England. 



Thalictrum flavum L. Wressle, E.R. 



Berberis vulgaris I>. Plentiful between Knottingley and 



Womersley in the roadside hedges. 

 Papaver somniferum L. Canal-side, Woodlesford ; Sandal. 

 Corydalis lutea DC. Old wall in the Abbey ground, Knares- 



borough, 1884. 

 Arabis thaliana L. Knottingley. 



Sisymbrium orientale L. = columnae Jacq. Waste ground at 

 Sandal. (See Nat, vol. i., p. 230. First Series.) 

 ''^ Sisymbrium junceum MB. Waste ground at Sandal. 



Sisymbrium sophia L. Knottingley ; Sandal. (Flamborough, 



P. Inchbald.) 

 Sinapis alba L. Clover field at Methley. 

 ^' Sinapis arvensis v. orientalis Murr. Sandal. 



Diplotaxis tenuifolia DC. Old walls at Pontefract Castle, 1885. 

 Eruca sativa Lamk. Quarry and waste ground at Sandal. (See 



Nat, vol. i., p. 204.) 

 Camelina sativa Cr. Clover field at Methley. 

 « .-f ifeslia paniculata Desv. Clover field at Methley. 

 ^ Rapistrum orientale DC. Sandal. 



Eaphanus sativus L. Footpath-side, Methley. 

 ^' Lepidium draba L. Waste ground at Sandal. 

 Reseda odorata L. Oat field at Stanley. 

 '''' Saponaria vaccaria L. Potato field at Lofthouse ; one plant. 

 Waste ground at Sandal ; plentiful. Clover field at Methley ; 

 frequent. (Wetherby, J. S. Wesley, 1879.) This species is 



Naturalist, 



