I855-] SUGGESTIONS AND QUERIES. 63 



the proportion of the Umbelliferae are ,;f J8 =^- ; for, without 

 one knows the whole numbers, one cannot judge how really 

 close the numbers of the plants of the same family are in two 

 distant countries ; but very likely you may think this super- 

 fluous. Mentioning these proportional numbers, I may give 

 you an instance of the sort of points, and how vague and 

 futile they often are, which I attempt to work out . . . ; 

 reflecting on R. Brown's and Hooker's remark, that near 

 identity of proportional numbers of the great families in two 

 countries, shows probably that they were once continuously 

 united, I thought I would calculate the proportions of, for 

 instance, the introduced Composite in Great Britain to all the 

 introduced plants, and the result was = . In our abori- 

 ginal or indigenous flora the proportion is ; and in many 

 other cases I found an equally striking correspondence. I 

 then took your Manual, and worked out the same question ; 

 here I find in the Compositae an almost equally striking 

 correspondence, viz. -^^ = \ in the introduced plants, and *f g % 

 5= -J- m tne indigenous ; but when I came to the other 

 families I found the proportion entirely different, showing 

 that the coincidences in the British Flora were probably 

 accidental ! 



You will, I presume, give the proportion of the species 

 to the genera, i.e. show on an average how many species each 

 genus contains ; though I have done this for myself. 



If it would not be too troublesome, do you not think it would 

 be very interesting, and give a very good idea of your Flora, 

 to divide the species into three groups, viz. (a) species com- 

 mon to the old world, stating numbers common to Europe 

 and Asia ; (b) indigenous species, but belonging to genera 

 found in the Old World ; and (c) species belonging to genera 

 confined to America or the New World ? To make (according 

 to my ideas) perfection perfect, one ought to be told whether 

 there are other cases, like Erica, of genera common in Europe 

 or in Old World not found in your area. But honestly I feel 



