The Study of Plant Life

by Marie Carmichael Stopes

There are maps of the whole of England, made by the Government, which show all the roads and houses, the chief rocks, hills, ponds, and so on. The geologists have taken these maps and added to them details of the kinds of rock and soil of which the land is built. If now we take fresh copies of the “ordnance” maps, as they are called, and put on them all the plants growing in different associations, we can compare the resulting “plant-maps” with the land-maps of the geologists, and I think you will be surprised to find how much the plant-maps and land-maps correspond.

To do this on a large scale, however, is far too big a piece of work for one person, or a few people, to attempt. We can only do some small piece of work on one area which will show how the rest is done, and yield some interesting details.

Let us suppose, for example, that the moor east of Settle is to be mapped. First get an ordnance survey map on a large scale—25 inches to the mile is the best, but the 6 inches to the mile will do. On the map are marked all the walls, streams, and even some of the bigger trees, so that it is easy to find on it the exact spot where you are standing. For working you should cut the sheet up into at least eight pieces, of regular size and shape, and use one of these at a time in the field.

First get to know the part you are to work on later in a general way, noting the chief plants and in what way they are associated.

Be careful in working to keep your sheets in regular order, and begin with the one at the bottom left-hand corner of the whole map. Find the exact spot on the ground which is represented by the point of the bottom left-hand corner of your first sheet, and put a white stake into it at least two feet high; it is better if you add a little red and white flag, so that you can see it from a distance. Then find each of the other four corners of your small sheet, measuring the distance from a wall or tree if need be, and put in each a white stake similar to that marking the first corner. If your map is on the 25-inch scale, and you have cut it into sixteen equal pieces, you will find that the area staked out on the ground represented in one piece is not so large but that you can see over it, and by walking about within it, get all the features of the plants growing there mapped out on to your sheet. In studying the different patches of plants, you will find that, as a rule, in each there is one important plant which grows in great numbers, while there are many more scattered and less important species growing with it. Such patches of plants growing together may be called Associations, and in mapping we only pay attention to the chief of these. In a patch where cotton-grass is the most conspicuous thing, there may be also half a dozen small grasses and plants growing with it, in which case everything but the cotton grass would be ignored in the mapping, and the association called the “cotton grass” association. Similarly, a patch where heather is the most important plant would be called the heather association. Sometimes you may find two or more plants growing together which seem to share the area between them, so that it is impossible to tell which is the chief one; in such a case where, for example, heather and bilberry are apparently equally important, the association would be described as “heather-bilberry.” For the sake of reference, lists should be kept of all the plants of less importance growing in the associations, though they are ignored in the mapping.

At the beginning it is wise to go over the area and find out roughly how many chief associations there are in it, and to make out a list of them. Then choose either a colour or a sign to represent each of them in the mapping,—a colour will generally be found to be clearer and more effective in the finished map, though a sign is very useful for the field-work.

When all these preliminaries are finished, begin the actual mapping by going very carefully over the different patches in the staked-out area of one piece of the sheet. From the details already printed in the ordnance survey map, you will generally be able to find the exact position of the patches of plant associations (unless they are very small, when they must be ignored), and you should soon be able from the help of the given details to fill in the shape of the patches by the eye. If in any case this is difficult, a 5-foot rule and a string of 20 feet or 30 feet marked out into 5 feet and 1 foot lengths will be found very useful. From the actual measurements you will then get, it is easy to find how much will represent them on the map by the simple sum:—1,760 actual yards are represented by 25 inches on the map, so that 16, 10, or whatever number of feet you require will be represented by (25 in. x 10 in.)/(1,760 x 3) or (25 in. x 16 in.)/(1,760 x 3) and so on.

Do all your field-work in pencil, and take notes in a “field-book” as you go, so that you will be able to copy out a neat, correct map at home in which to colour in the associations and outline the patches with waterproof ink. When one of the sheets is done in this way, stake out the area for the next, and so on, till you have all the sheets finished. Then paste them together again on a piece of muslin in their proper order, and you will have a complete “plant-map” of one definite, though small, area. This can be easily compared with a geological map of the same area, though the geological one will be on a rather smaller scale (best 6 inches to the mile), and you will see how the patches of plants frequently follow the arrangement of the rocks. This does not show so clearly on too small an area; the larger the district you can cover the better.

To work from an ordnance survey map is the easiest way of proceeding, but if you like to combine the plant study with a little simple survey work, it is quite possible to make the map from the very beginning. This is not generally worth the trouble, except in cases where you find a rich and interesting area which would repay very careful mapping on a larger scale than the survey have published. For example, it would be a very good plan to choose some small area, and in it stake out exactly 100 feet square. Along the sides plant smaller stakes every 20 feet, and map all the details very carefully on to mathematical paper on the scale of either 5 inches or better, 10 inches to 100 feet. Such an area would well repay the trouble of repeated mapping at different times of the year. If you have a series of maps of the exact area every two months, for example, you will be able to see from them very well the succession of plants throughout the year, and how the associations change according to the seasons.

Another thing that should go with the mapping is the plotting out of “sections” through the irregular land, which will show clearly how frequently the plants growing on any spot are determined by the level of the spot and its consequent relation to the water supply. The most striking case of this kind is that of a section through a pond or stream and its banks. Unless you have a boat at your service, you will have to choose a stream where two people can meet across it from the banks, or else content yourself with going out only as far as you can wade.