ZOOLOGICAL AND BOTANICAL ASSOCIATION. 227 



in winter) often wanders inland, and seeks refuge in such places. On 

 the other hand, the common rat does not confine its excursions to the 

 land. Thus a gentleman hooked a rat by an artificial fly, and it was 

 probably this species, though he calls it a water rat ; at any rate it is, 

 doubtless, the common rat to which are due the heaps of shells of the 

 Anodon and Paludina, which may often be seen on the banks of rivers 

 with the sides of the shells broken away, in order to get at the soft 

 parts ; they always abound in these places, but how they manage to fish 

 the shells out, I cannot say. 



For details of Plates XXIII. and XXIV. see the Description of Plates, 

 which will be given as an Index at close of volume. 



David Moore, A. L. S., Associate Member, read a paper — 



OBSERVATIONS ON SOME PLANTS CONSIDERED BY M. DE CANDOLLE TO BE ALIEN 

 AND INTRODUCED INTO BRITAIN. ALSO NOTICES OF SOME NEW 8PECIES 

 TO THE IRISH FLORA, WITH ADDITIONAL HABITATS OF OTHERS, HITHERTO 

 8TJPP0SED TO BE RARE. 



In no other department of British Botany have so great advances been 

 made of late years as in that known by the term " geographical distri- 

 bution ;" a' term which, those acquainted with the subject know, com- 

 prises several considerations connected with the habitats of plants, which 

 to the ordinary reader it does not fully convey. It is not only the geo- 

 graphical area over which a species spreads, and its prevalence within 

 that area, but also the geographical position on the configuration of the 

 earth's surface, climatial influences, causes, and effects in the establish- 

 ment of species, whether spontaDeous to the soil or only there natura- 

 lized, along with many other important facts. In short, it might not 

 be too much to say of it, as has been said of the introduction of the na- 

 tural system of classification to Botany at large, that in relation to histo- 

 rical botany it renders it a science. 



I need hardly state here, before so many distinguished naturalists, 

 that in these countries Hewit Cottrell "Watson has led the way, which 

 M. de Candolle, in his great work, " Geographie Botanique," states he 

 has done judiciously and welL In Ireland comparatively little progress 

 has been made in that direction, and a wide field yet remains to be 

 explored by industrious collectors of materials, to be subjected to a 

 generalizing mind, before a good history of the geographical distribution 

 of the plants of this country can be given to the public. Mr. Watson 



