CONCLUSION. ; 577 
probably further prolonged in America than in the Old World; 
that as Composite began to disappear from these tropical regions 
which thenceforth opposed to them impassable barriers, they be- 
came rapidly differentiated and multiplied both northward and 
southward, with greater structural divergences in the Old World 
than in the New, owing to the isolation being more complete in 
the former than in the latter; that those forms, those more or less 
differentiated races which had reached and accommodated them- 
selves to high northern latitudes or mountain altitudes retained 
Some means of communication and interchange between the Old 
and the New World long after it was broken off in the warmer 
parts of the globe; and that the homes where Composite now 
flourish in the greatest luxuriance of specific variety and individual 
numbers appear to be, tropical America exclusive of the great 
alluvial low grounds and forest regions, the United States, South 
Africa, the Mediterranean region, West Central Asia, and extra- 
tropical Australia. 
The above paper had already been ordered for printing by the 
Council of the Linnean Society, and the corresponding portion of 
the * Genera Plantarum ' placed in the printer's hands, when I 
received from Mr. C. B. Clarke, who has for many years been 
studying on the spot the flora of Bengal, a detailed enumera- 
tion of the Composite of that province, with many valuable notes 
on their synonymy and on the cireumseription of their genera and 
species. The views expressed in this paper so far coincided with 
those I had already entertained in working up the order, that I 
did not think it worth while to enter into the reexamination 
which would be necessary for a careful comparison ; but as it was 
only fair to Mr. Clarke that he should have due credit for his in- 
vestigations, I read his letter at a meeting of the Society, and 
applied to him for leave to print his observations as an appendix 
to the present notes. He has, however, observed in reply that 
his communication was only intended as an aid to me in working 
out the order, and not sufficiently matured for publication in its 
present form. Acknowledging, therefore, the full value of these 
critical notes, I have reserved them for the use of the editora of 
the new * Flora Indica,’ now, it is hoped, in a state of steady 
progress. 
