EXPERIMENTAL EVOLUTION 155 



ing them is not too great, it is a distinct advantage to move a number of 

 individuals in the same block of earth. The transfer of mature plants is 

 inadvisable, except for those perennials which can not readily be secured in 

 an early stage. This naturally does not apply to woody plants, evergreen 

 herbs, mosses and lichens ; the last two may be transferred at any time with 

 satisfactory results. Each culture is carefully marked with stakes, and 

 definitely located by means of landmarks. 



Fig. 46. Series for producing hydrophytic forms under control: 

 1, amphibious; 2, floating; 3, competition; 4, submerged. 



Reciprocal transfers may be made by means of seed or plant. Since the 

 experiment is a complex one, all the care possible should be taken to make 

 sure that the plants become established in the reciprocal situations, and con- 

 sequently, it is often advisable to transfer both seeds and plants. Reciprocal 

 transfer is of paramount value in solving the problem which bog plants 

 present. A slight modification of the method makes it possible to obtain 

 experimental evidence of the polyphyletic origin of species in consequence 

 of adaptation. In an experiment mentioned elsewhere, the transfer of 

 Knhnistcra purpurea to the area occupied by K. Candida, and vice versa, is 

 designed to show whether one has been derived from the other. If the two 

 species are moved into an area which contains more water than that usually 

 occupied by K. purpurea, and less water than is found where K. Candida 

 habituallv grows, the resulting modifications will throw much light upon the 



