PREFACE. 



not what there is, but what there is not, in the way of rarity. 

 Those who wish for rarities must go far to find them. The causes 

 before referred to, will account for the disappearance of many of 

 them ; the extermination of others has been often ascribed to the 

 indiscriminate rapacity of collectors themselves, and the growing 

 passion for collecting. However, for purposes of study one plant 

 is as good as another ; all that is further necessary is sufficient 

 variety, and many a humble weed is possessed of structural pecu- 

 liarities as instructive and interesting as any to be found in plants 

 of less frequent occurrence. Those who would know the geo- 

 graphical range of the vegetation round London will find in every 

 locality the characteristic plants of the same, duly recorded ; but to 

 the mere collector the constant repetition of the same thing in one 

 part of the country and of another thing in another part will 

 appear tedious and superfluous. Given a series of plants, and the 

 nature of the locality which produced them can be determined at a 

 glance. In addition to the series common to certain localities, many 

 of them possess some speciality or other peculiar to themselves : 

 the black Bog Kush grows on Bagshot Heath ; the marsh Cinquefoil, 

 on Elstead Common ; the ivy-leaved Campanula (Wahlenbergia) 

 grows at Witley Lagg ; the Bog Gentian on Chobham Common, and 

 so forth : The Fritillary is at home in the basin of the Thames ; 

 the white Beak Bush is rare, except on the sandy heaths of S.W. 

 Surrey. Many plants are of uncertain appearance in their respective 

 localities ; especially such as are designated colonists. They appear 

 and disappear, according to the nature of the crops, &c. Excess of 

 heat, of moisture, of drought, or the contrary may exercise an 

 influence in one way or the other ; persons therefore, visiting 

 localities in search of any plant in particular, must not count too 

 surely upon success in finding it. 



One difficulty with which the general student may have to 

 contend is the nomenclature adopted in the Catalogue of 1874, with 

 which this publication is in accord. Of 237 species additional, 

 nearly all are promotions from the rank of varieties. The total for 

 all Britain, exclusive of Charads and minor Cryptogams, amounts to 

 1665, of which number no less than 1250 are computed to occur 



