154 _.. THE PLANT 
been produced by experiment. Modification or transfer is made in the usual 
way, but reciprocally, i. e., the original form is transferred to the habitat of 
the ecad, and the latter to the habitat of the former; or the shade in which 
some individuals of the ecad are growing may be destroyed, and at the same 
time individuals of the type may be shaded. Both transfer and modification 
may be applied to the same species, but since the same measured change of 
factor can be obtained in either way, the use of both is undesirable, with the 
exception of the rare cases where they serve as checks upon each other. 
The transfer of a seed or plant is so much simpler and more convenient 
that this method is the one regularly used. It sometimes happens, however, 
that a change of water-content or light intensity is readily and conveniently 
made, and is desirable for other reasons. 
It is evident that both transfer. and modification require that the factor 
records of the various habitats or areas be as full as possible, at least so far 
as water-content, humidity, and light are concerned. In the case of the 
areas that are to be modified, these factors are determined before the change 
is made. Afterward they are read from time to time during the growing 
season, and are also checked by readings made near at hand in the unmodi- 
fied formation. The readings made in the beginning should correspond 
closely to the check readings, but in case of disagreement the latter are to 
be taken as conclusive. ; 
193. Transfer. After the species to be used for experiment has been 
chosen, the various habitats or areas selected, and the direct factors meas- 
ured by instruments, the actual transfer of the individuals is made by means 
of seeds, preferably in autumn, though the results are practically the same 
if seeds are kept over the winter and planted at the opening of spring. The 
natural method is to scatter the seeds in the place selected, as though they 
had been carried by the usual agents of migration. The mortality is usu- 
ally great in such case, however, and the chances of success are increased 
by actually planting the seeds. This is the method which has been used in 
making cultures of species of the European Alps on the summit of Mount 
Garfield in the Rocky mountains. The number of seeds used is recorded in 
order to obtain some estimate of germination and competition. While the 
use of the seed or disseminule possesses the great advantage of making the 
experiment essentially a natural one, the transfer of rosettes, seedlings, or 
young plants makes the results more certain, and consequently saves time, 
even though the actual transfer is somewhat more difficult. It is hardly 
iecessary to point out that the removal of the plant should be made with the 
greatest care. The best success is obtained by making the transfer on cloudy 
or rainy days, and when shade plants are to be placed in sunny situations, 
they should be transplanted late in the afternoon. When the task of carry- 
