illustrating the Distribution of Plants. 2 1 



graphy are directly and inseparably connected in the relation 

 of cause and effect. Here, therefore, we most need to call in 

 the aid of maps ; and here, fortunately, we shall find them 

 most easily applicable, and at a cost comparatively small. As 

 in this investigation we represent vegetation in the aggregate, 

 not according to technical details, a single map may be made 

 to include the whole flora of a country ; and one in which its 

 physical peculiarities are well represented should be selected 

 for the purpose. On such a map the divisions and sub- 

 divisions into vegetable regions could be marked nearly in 

 the same manner as we see the extent of kingdoms, counties, 

 &c, laid down. Since nature, however, does not admit the 

 precise and abrupt lines of demarcation seen in political and 

 parochial divisions, it would be wiser to avoid attempting 

 boundary lines; shadings or conventional marks being sub- 

 stituted instead, such as might be gradually intermingled in 

 proportion to the intermingling of the real vegetation. Co- 

 lours might be used in place of the marks, but would scarcely 

 answer so well ; or the names of places in different characters 

 could represent their vegetation. 



I have remarked above, that nature does not admit of pre- 

 cise boundary lines; yet hitherto lines have been almost in- 

 variably resorted to for the purpose of indicating distribution 

 in botanico-geographical maps. In the distribution of species 

 (and other superior groups necessarily follow the same laws), 

 we usually see a definite extent of country over which each 

 respective species is copiously scattered. Whichever way 

 we depart from these head quarters, the number of specimens 

 or individuals is found to decrease; large intervals then 

 occur without a plant of the species being seen ; and, finally, 

 a few localities may be found, scores of miles apart, and with- 

 out a single specimen between them. How can such dis- 

 tribution be represented by lines ? If we connect the ex- 

 treme localities by lines, they must be drawn across, and also 

 include, a large tract where the plant does not grow ; and 

 thus they will convey to the eye an appearance of abrupt 

 termination which has no real existence. Signs more or less 

 thickly placed, and shadings more or less intense, are ob- 

 viously far better adapted to depict the realities of nature. 

 Thus, we come nearly to the plan suggested in an early 

 Number of this Magazine ; and if the skeleton maps there 

 proposed can be carried into effect, they will form a most 

 important aid to the geographic botanist. See II. 342. 



Ditton Marsh, Surrey, Nov. 1835. 



c 3 



