Lees : On the Proposed New Map of Yorkshire. 55 



Our map may be made (without overloading, it with detail — avoid 

 that !) to show two other very important factors in the distribution of 

 plants besides the geological one. To one of the conditions of division 

 which have been named, — viz., that the boundaries of the adopted tracts 

 must be well defined and easily recognisable ; I have, however, this to 

 remark : I fear it cannot be done if " roads, railways, and rivers, or, 

 failing these, parish boundaries," are to be taken, for they nowhere 

 coincide exactly I fear, at any rate for far, with " the sinuosities of 

 the lines of strike " any more, I may add, than do the river-basin 

 divisions. If our divisions are to be geological, let them be geological, 

 and as accurate as map-scale will allow as to strike-lines, and trust 

 (for we must anyway leave something to the intelligence of the user 

 of the map) to the finder of a plant near a border-line to decide on 

 what stratum he gathered it. 



IV. Plan of Division proposed. — My plan is this : to make the 

 map of practical value in four ways, and upon it I would show clearly 

 four things. 



1. — The jive vice-comital divisions used in H. C. Watson's works on 

 Topographical Botany, viz : N E, fifth ; S E fifth ; N W, mid- 

 west, and S W, fifths. Show these clearly by some bright distinctive 

 lines. For artificial divisions of area they are quite small enough for 

 the purpose of making any census likely to be useful. Very few species 

 of plants save the 380 ubiquitous ones, such as the daisy, dandelion, 

 &c., will be found in all the divisions, and where one is absent there 

 will nearly always be found a factor of distribution wanting also, and 

 accounting for it. 



2. — Bring prominently out the two great physical features of the county. 

 The first of these is its division into an east and west slope (in 

 section) by the great summit ridge of the Pennine chain that cuts off 

 the western fourth. Mark this great water parting very boldly in 

 some way — by a broad, deep blue line, say. You would find four 

 rivers running S W : all the rest south-by-east, or east. From the 

 fact of the summit-ridge cutting off winds, arresting moisture, &c., 

 there is a different climate, and a different, more atl antic, flora upon 

 the west slope to what there is upon east. 



'The second great physical feature is the cutting in half of the 

 eastern portion thus formed, by the Ouse and alluvial vale of York. 



This tract, a few miles on each side of Ouse from Goole to about 

 Northallerton, has a climate of its own, a soil of its own, and a 

 peculiar flora of its own, complex in its character because made up in 

 several ways : just as the detritus from the western hills and the 



