THE CANADIAN ENTOMOLOGIST. 375 



The impression of the greater abundance of these apically dehiscent 

 forms in certain of the major divisions of the earth's surface seemed to be 

 established by a consideration of the distribution of the forms themselves. 

 Thus, of the monocotyledonous genera of the Solanum-Cassia type, 1 1 of 

 the 19 were found to be endemic in South America, while another has 8 of 

 its 10 species there. Of the Dicotyledons, i r of the 40 genera are endemic 

 in South America, and 7 others occur there, in five of the cases represented 

 by the most of their species. Thus 57.8 per cent, of the monocotyledonous 

 genera are endemic in South America, and 63.1 per cent, occur there) 

 while of the dicotyledonous genera 27.5 per cent, are endemic and 45 per 

 cent, occur there. Altogether 30 of the 59 genera, or 50.5 per cent., 

 occur in South America. This type is also strongly represented in the 

 Indian and Australian region, while ekewhere it occurs but sparingly. 



The Dilleniaceous type shows a very similar distribution, but is found 

 most abundantly in the Indian instead of the tropical American region. 

 The Melastomataceous type is almost exclusively South American and 

 Indian. 



These facts certainly seem to indicate the greater abundance of these 

 floral forms in the South American, Indian and Australian regions. It 

 early became evident, however, that the problem of the geographical 

 distribution of these forms is one very difficult of approach. The 

 apically dehiscent types clearly showed a more or less localized distribu- 

 tion, but it was also seen that in the region where the apically dehiscent 

 genera are most abundant the flora as a wliole also appears richer, and it 

 became clear that any valid conclusions concerning distribution must be 

 based on statistical comparisons, not merely of the apically dehiscent forms, 

 but of all genera as well. It seemed most advisable to mike the com- 

 parison by genera, and to take the data for the purpose from Engler and 

 Prantl's Die Natijrlichen Pflanzenfamilien. 



The earth was divided into fourteen floristic regions patterned after 

 those of Drude, but of necessity limited more arbitrarily, as follows : 



I. Tropical Regions. 



1. Tropical African Region. 



2. East African Island Region. 



3. Indian Region. 



4. Tropical American Region. 



