APPENDIX. No. \'. 123 



in the Paper above quoted; a ratio which seems to be confirmed by his own 

 extensive herbarium. 



I had remarked, however, in the Essay referred to, that the relative numbers 

 of these two primary divisions in the equinoctial parts of New Holland appeared 

 to differ considerably from those which I had regarded as general within the 

 tropics; dicotyledones being to monocotyledones only as 4 to 1. But this 

 proportion of New Holland \ery nearly agrees with that of the Congo and 

 Sierra Leone collections. And from an examination of the materials com- 

 posing Dr. Roxburgh's unpublished Flora Indica, which I had formerly 

 judged of merely by the index of genera and species, I am inclined to think 

 that nearly the same proportion exists on the shores of India. 



Though this may be the general proportion of the coasts, and in tracts 

 of but little varied surface within the tropics, it seems at the same time pro- 

 bable from Baron Humboldt's extensive collections, and from what we know 

 of the vegetation of the West India islands, that in equinoctial America, in 

 tracts including a considerable portion of high land, the ratio of dicotyledones 

 to monocotyledones is at least that of 11 to 2, or perhaps nearly 6 to ] . 

 Whether this or a somewhat diminishetl proportion of dicotyledones exists 

 also in similar regions of other equinoctial countries, we have not yet sufficient 

 materials for determining. 



Upon the whole, however, it would seem from the facts of which we are 

 already in possession, that the proportions of the two primary divisions of 

 phsenogamous plants, vary considerably even within the tropics, from cir- 

 cumstances connected certainly in some degree with temperature. But there 

 are facts also which render it probable, that these proportions are not solely 

 dependent on climate. Thus the proportion of the Congo collection, which is 

 also that of the equinoctial part of New Holland, is found to exist both in North 

 and South Africa, as well as in Van Diemen's Island, anil in the south of Europe. 



It is true indeed that from about 45° as for as to 60', or perhaps even to 

 G5° N. lat. there appears to be a gi-adual diminution in the relative number 

 of dicotyledones ; but it by no means follows, that in still higher latitudes a 

 further reduction of this primai-y division takes place. On the contrary-, it 

 seems probable from Chevalier Giesecke's list of the plants of the west coast of 

 Greenland,* on different parts of which, from lat. 60° to 72°, he resided several 

 * Article Greenland, in Brewster's Edinburgh Encyclopedia. 



