174 Snii/h : The Use of Maps in Bolany. 



recorders with a list of plants which they are asked to record. 

 The maps are sub-di\ided by squares into small areas, so that 

 the position of a sing-le plant or g-roup of plants of a species can 

 be marked with great accuracy. The district is a g-ood one for 

 examining the upper limits of lowland plants and the lower 

 limits of Alpine species, and the object is to ascertain these and 

 other facts regarding the distribution of plants. It is not 

 sufficient to state that some particular plant occurs in a 

 Watsonian vice-county, or in a parish, river basin, or some 

 similar division of Britain. It is a familiar fact in Yorkshire 

 that there may be considerable variations in altitude and in 

 the geological formations and soils within a single square 

 mile ; these have each an influence on plant growth, because 

 the}' bring about changes in the climate and the soil conditions. 

 The occurrence of a particular species may also be due to the 

 presence or absence of trees or shrubs, and may have little 

 relation to altitude or latitude, except in so far as these influence 

 the tree-growth. The mere recording of the stations for a 

 species may not be scientific work of a high order, yet if a large 

 number of records were correlated by a competent organiser, as 

 in the case just mentioned, results of importance could be 

 attained. For records of this kind the one-inch Ordnance maps 

 are too small, and the six-inch or twenty-five-inch maps would 

 be necessar}-. The expense is an objection which will be 

 considered later. The suggestions of Mr. Cosmo Johns and 

 Mr. Harker will be seen to apply definitely where map-records 

 of this kind are made, and one or other system should be 

 adopted in the work. We should also like to re-emphasise Mr. 

 Marker's advice to make the record on the spot. 



Recording of plant associations. The choice of a suitable 

 scale of map depends on whether the association to be recorded 

 covers (or is likely in every case to cover) a large area or a 

 small one. If, as in the Yorkshire botanical surveys. Heather, 

 Grass, Cotton Grass, and other large moorland associations, 

 with three or four types of woods are the only things shown on 

 the map, then a careful observer may find the one-inch map 

 sufficient. Yet almost all who are now engaged in similar 

 work find the six-inch maps more useful, because they contain 

 so many more landmarks by which to determine one's position. 

 There need be no hesitation in strongly recommending the six- 

 inch maps for the work of local societies, and, as Mr. Cosmo 

 Johns states, these are already in use at Shefl'ield. There is, 

 however, a system of botanical survey for which even the six-inch 



Naturalist, 



