234 -L' ie ^ ris "- Naturalist. December, 



soil relations scattered through the text, make without doubt 

 one of the most interesting and valuable features of his 

 book. 



Even the severest of reviewers might condone a good deal 

 of incompleteness in a work of such magnitude and intricacy 

 as Irish Topographical Botany ; but there is really nothing of 

 this kind to call for indulgence. The work has been not only 

 rapidly done but thoroughly done, so thoroughly, I believe, as 

 to surpass the results achieved in Great Britain in a similar 

 field of inquiry by the labours of many botanists spread over 

 a period of fully twenty years. The first edition of Watson's 

 Topog7 r aphical Botany was completed in 1874, the second 

 appeared in 1883, and the ninth edition of the Lo?idon 

 Catalogue, showing the latest published statistics of comital 

 plant distribution for Great Britain, appeared in 1895. This 

 last edition of the London Catalogue, then, presents us with 

 the fruits of some twenty years of field work by British 

 botanists, and a comparison of this catalogue with Mr. 

 Praeger's book would seem to warrant the conclusion that 

 his five years of skilfully planned work in Ireland have 

 accomplished more than twenty years of desultory effort in 

 Great Britain. 



In endeavouring to estimate the comparative thoroughness 

 of the botanical surveys of Great Britain and of Ireland we 

 may take as basis the number of species ascertained to occur 

 in all the comital or vice-comital divisions of each of the two 

 areas to be compared. It appears from Mr. Praeger's very 

 lucidly arranged Table of Distribution, that out of a total 

 Irish flora estimated by him at 1,020 species, 260 are 

 ubiquitous, that is to say, known to occur in all forty divisions 

 of the island. 1 The question then becomes, how many species 

 out of the total British flora, taken at 1,500, should we expect 

 to find recorded as ubiquitous if the botanical survey of Great 

 Britain were as well done as that of Ireland ? 



The problem is by no means reducible to a case of the Rule 

 of Three, since the proportion of ubiquitous species to the 

 total flora must vary with the variation of several conditions 



1 The number of species actually ubiquitous in Ireland, though not 

 yet shown to be so, is no doubt much larger than this, since it appears 

 from the Irish Distribution Table that some 45 species are at present 

 on record for 39 out of the 40 divisions. 



