862 Wilson.—Plant Distribution in the 
In the present communication the relative prevalence of plants will be 
indicated by the use of certain terms. These will be employed in the 
following order:— 
1. Very abundant. 
2. Abundant. 
3. Frequent. 
4. Generally distributed. 
5. Sparingly found. 
6. Occasionally found. 
No numerical value can be attached to these terms, but as far as possible 
the same term will always be used to express the same degree of prevalence. 
It will be noticed that the term ‘ dominant ’ has been omitted from the above 
list. The use of this term is considered unsatisfactory in this sense. In the 
following description the use of this expression will not necessarily indicate 
that the plant is very abundant, but that its presence has a great and well- 
marked effect on the immediately surrounding vegetation. Every plant 
obviously influences the plants in its vicinity to a certain extent, but the term 
‘ dominant ’ is reserved for extreme cases in which the existence of the 
surrounding species is threatened or even rendered impossible. 
In this paper the plant names adopted are those given in the c Manual of 
British Botany’, by C. C. Babington, ninth edition, edited by H. and J. 
Groves, 1904. The Mosses are named in accordance with the ‘ British Moss 
Flora’, by R. Braithwaite, 1887. ‘The Hepatics of the British Islands,’ by 
H. W. Lett, 1902, has been used for naming the Liverworts. 
The Chalk. 
The woods on the Chalk soils in both of the districts investigated are 
fairly numerous, but usually not of great area. In almost all cases they are 
found on the sides of the dry valleys already referred to, since it is only in 
these positions that the Chalk is free from the overlying deposits. The 
soils vary considerably in depth ; while in some places the Chalk is barely 
covered, in others there is a considerable depth of soil upon it. Many 
of the woods examined extend over two or more different deposits, such, 
for example, as the Chalk and the Clay with Flints or the Chalk and the 
Thanet Sand, and the Chalk soils probably vary in composition with the 
proximity of these other deposits. Considerable differences in depth 
of soil may also be found in one small woodland area. 
The composition of various Chalk soils is given by Hall and Russell in 
their ‘Report on the Soils and Agriculture of Kent, Surrey, and Sussex ’ ( 7 ). 
The percentage of calcium carbonate, although variable, is usually high ; 
as a result of this fact these soils, even in woodland areas, are rarely or never 
acid. Mechanical analysis shows that the amount of finely divided material 
(fine sand, silt, and true clay) is usually large. 
