210 PLANT PHYSIOLOGY AND ECOLOGY 



in the spring. In this case invasion is ordinarily delayed, owing 

 to the removal of accumulated seeds and propagules. The treat- 

 ment of denuded quadrats upon succeeding visits is the same as 

 for permanent ones. Since denuding practically makes a new 

 habitat, the factors which control invasion can be found only 

 by taking readings within the denuded area. Such readings are 

 of the greatest value when they can be compared with those of 

 an adjoining permanent quadrat. 



225. Transects. The transect is a cross-section of vegetation. 

 It is practically an elongated quadrat, extending through a station, 

 a formation, or a series of formations. Unlike the quadrat, it is 

 designed to show in a graphic manner the differences in structure 

 between two or more contiguous areas. While the quadrat is 

 always located in a homogeneous area, the transect traverses areas 

 more or less unlike, and is plotted with especial reference to topog- 

 raphy. The transect is principally used to bring out the differences 

 between zones, and between those groups of individuals called 

 societies, communities, and families. With respect to dimension, 

 transects are distinguished as line, belt, or layer transects. Belt 

 transects are permanent and also denuded. The last belongs 

 properly to investigation and hence is not discussed here. 



226. The line transect. This is the form employed when only 

 the more striking differences in structure are sought. It is espe- 

 cially adapted to elementary study, on account of the relative 

 ease with which it may be run. It is ordinarily used for an entire 

 formation or for a series of them. A simple line transect is made 

 by establishing the desired points and then recording the plants 

 pace by pace along the line between them. A more accurate 

 method is commonly used to give detailed results. In this tapes 

 exactly like quadrat tapes but 10, 50, or 100 meters long are used. 

 The transect is located in the area to be studied by running the 

 tape from one landmark to another, and fastening it here and 

 there by quadrat stakes. When the topography is not level, it 

 is necessary to obtain the length and angle of the slopes in order 

 that an exact outline map may be constructed. In noting 

 the plants that occur along the tape, every second vertical line 

 on the centimeter plotting paper is taken to correspond with the 

 tape. The individual that touches the latter is recorded to the 

 right or left respectively, and within the centimeter square that 

 corresponds to the particular decimeter interval of the tape. When 



