186 CHLORIS MELVILLIANA.
notice, likewise, as a third cause of the delay, the greater extent of my original plan, ^yhich included remarks on the state and relative proportions of the primary divisions and natural orders contained in the list ; a comparison with the vegetation of regions of nearly similar climates ; and obser- vations on the range of those species common to Melville Island and other parts of the world. Towards the com- pletion of this plan I had made considerable progress. But to have satisfactorily treated some of the subjects referred to would have required more time than I have had it in my power to devote to them, and in several cases better materials than I have hitherto been able to obtain.
I have consequently found it necessary to rehnquish, for the present, this part of my plan,i and to confine myself to a systematic list, adding only characters and descriptions ccixiii] of the new or imperfectly known genera and species ; the only indication left of my intention to treat any of the subjects alluded to being a greater number of references
1 I sliall here offer a single remark on the relative proportions of the tu'o primary divisions of Phsenogamous plants.
In my earliest observations on this subject I had come to the couclusioa that from 45° as far as 60° or perhaps 65° of north latitude, the proportion of Dicotyledonous to Monocotyledonous plants gradually diminished. {Flmders voi/. 2, p. 538. A7ite,p. 8.) But from a subsequent examination of the list of Greenland plants, given by Professor Giesecke (Art. " Greenland," in Brewster's 'Edinburgh Encyclopaedia'), as well as from what I had been able to collect respecting the vegetation of alpine regions, I had supposed it not improbable that in still higher latitudes, and at corresponding heights above the level of the sea, the relative numbers of these two divisions were again inverted {Tucke/s Congo, p. 423. Ante, p. 103) ; in the list of Greenland plants referred to,Dicotyledones being to Monocotyledones as four to one, or in nearly the equinoctial ratio ; and in the vegetation of Spitzbergen, as well as it could be judged of from the materials hitherto collected, the proportion of Dicotyledones appearing to be still farther increased.
This inversion in the cases now mentioned was found to depend at least as as much on the reduction of the proportion of Gramineae, as on the increase of certain Dicotyledonous families, especially Saxifrageae and Crucifera3.
The Flora of Melville Island, however, which, as far as relates to the two primary divisions of Phaenogamous plants, is probably as much to be depended on as any local catalogue hitherto published, leads to very different con- clusions ; Dicotyledones being in the present list to Monocotyledones as five to two, or in as low a ratio as has been anywhere yet observed ; while the proportion of Grasses, instead of being reduced, is nearly double what has been found in any other part of the world (see Humboldt, in 'Diet, des Sciences Nat.,' torn. 18, table at p. 416) ; this family forming one fifth of the whole Phsenogamous vegetation.
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