236 Methods of Surveying Vegetation. 
scattered plants of Obione portulacoides (0) and Salicomia radicans 
( + ) on their edges. It also shews that the SI. G. plain is practi¬ 
cally flat for most of its extent, and slopes gradually up towards the 
left and towards the top to higher ground occupied by G. Sd. In 
the top right hand corner are patches of intermediate associations 
in which G., SI., and Sd. are variously mixed. At the extreme top of 
the square three spurs, bounded by the 410 contour, project from 
the higher ground which is out of the map. These spurs are covered 
with Sd. G. in which the Sd. has a characteristic red (madder) colour. 
A few plants of Obione and S. radicans are found on the edge of the 
higher ground, while the SI. G. plain is quite destitute of them. 
Part of an irregular pan, largely bounded by SI. and SI. G., and 
whose bottom is at a distinctly higher level than that of the channel 
at the foot of the grid, appears in the top left-hand corner. 
It is not part of the purpose of this paper to discuss further 
the features exhibited by Fig. 80. But enough has been said to 
shew the kind of features that can be shewn, and the way in which 
in the detail of the information given on the smaller scale map- 
can be filled in. 
Plate XI. is from a photograph shewing the characteristic 
vegetation of the Bouche d’ Erquy. It is taken from near the 
extreme corner of the square and grid represented in Figs. 78 and 
80, looking over the square with the grid in the foreground. Most 
of the features shewn in the figures can be identified in the photo¬ 
graph. The G. Sd. association is on the higher ground and appears 
lighter, while the G. SI. is on the lower grouud and appears darker. 
A single grid-map can be used as a detailed sample of vegetation 
shewn on a larger map, or a connected system of grids can be con¬ 
structed, as in the case of the system of squares previously 
described, where it is desirable to make a detailed survey of a larger 
area. Fig. 80 belongs to such a system, which was chosen to 
exhibit the nature of the ground and the vegetation connected with 
a series of “pans” and ridges extending from the red SI. G. plain (of 
which the part shewn in the figure is one extremity) to certain deep 
supply channels, some 130 feet away. 
Finally it may be again remarked that the gridiron method is 
only available on fairly fiat or gently undulating ground, and that it 
is probably not worth applying except in such cases as that illus¬ 
trated, where there is a definite and considerable variation of the 
vegetation in the space of a few feet, in correlation with a similar 
variation of some one or more physical features. In the case 
