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 

 necessary 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- 



