180 THE FORMATION 
‘that all charts and photographs must bear the number of the reading as well 
as that of the transect. Physical factor observations are taken as often as 
the charts are made, and the results noted on the back of the chart sheet for 
purposes of ready comparison. 
The Denuded Transect 
223. The denuded transect bears exactly the same relation to a perma- 
nent one as that which exists between the denuded and the permanent quad- 
rat. While the permanent transect records the actual mutations due to 
changing physical factors or to competition, the denuded transect throws 
needed light upon the mobility and ecesis of the various species, and upon 
the nature of the competition between them. Denuded transects may be 
established wherever it seems desirable, after the strip has been properly 
charted and photographed. The most valuable results, however, are secured 
by locating each one alongside of a permanent one. The best plan is to lo- 
cate and chart two permanent transects a meter apart. A single view is then 
made of the two. One of them is denuded together with a strip 2 decimeters 
on either side, resulting in a denuded transect 5 decimeters wide. In chart- 
ing this during succeeding years, the entire width may well be plotted as 
long as the vegetation is open, but after it has again become well established, 
it is necessary to save time by confining one’s attention to the central deci- 
meter strip. Photographs can be made either of the permanent and denuded 
transects singly, or of the two together. The latter method has certain ob- 
vious advantages. Climatic factor readings can be made for both transects 
in common, but all those factors which are affected by the exposure of the 
soil surface must be observed in each. 
The Layer Transect 
224. This is a modification of the line transect, by means of which the 
vertical relations of plants are also shown, especially the tendency to form 
layers which is so regular a feature of forest formations. : Owing to the dif- 
ficulty of charting in three planes, belt transects do not lend themselves’ to 
this purpose. Because of the greater complexity, layer transects can rarely 
exceed ten meters in length except in those formations where layering is lit- 
tle or not at all developed. The simplest method is to establish a line tran- 
sect in the ordinary way, and then to record the height of each plant as its 
position is noted. This is done by means of a measuring stick ruled in deci- 
meters, which can be moved from interval to interval along the tape, or bet- 
ter, by two such sticks connected by tapes a meter long at every five deci- 
