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THE AMERICAN NATURALIST [Vol. XLV 



by seeds, in which case it is fairly clear that somatically 

 produced characters have been impressed upon the germ- 

 plasm and carried by it to succeeding generations. The 

 structural and functional features displayed by Semper- 

 vivum in these laboratory experiments are not adaptive 

 in any sense in contrast with those of Capsella, which are 

 direct responses. 



The actual transplantation of organisms from one lo- 

 cality to another, as a method of experimentation, prom- 

 ises the results of highest value and widest significance, 

 especially when taken in connection with analytical lab- 

 oratory cultures. This method of approach is one which 

 may yield evidence of the greatest value upon the influ- 

 ence of isolation and other geographical factors, but is 

 also one which allows the repetitive or mnemonic effects 

 to be evaluated. When supplemented by laboratory 

 analyses and cultures to determine the nature of altera- 

 tions induced, such methods promise results of the great- 

 est value. A series of plantations including locations from 

 mountain tops to the seashore has been established in con- 

 nection with the Desert Laboratory in accordance with this 

 idea, and in addition to the interchange of species from 

 the various localities a number of introductions have 

 been made from eastern America. Negative or positive 

 results of sufficient inclusiveness to permit analyses as to 

 the nature of the exciting agency and the permanence of 

 the response are yet available. 



Some of the characters called out by environic agencies 

 may be retracements, or regressions, as the reappearance 

 of spines in cacti, or they may be awakened latencies or 

 organizations de novo. Some of the responses may result 

 in sexual dimorphism, while in others the induced char- 

 acters may be sex-limited. The alterations induced by 

 external agencies may be cumulative or mutative as to 

 appearance or organization, and they may be permanent 

 upon first appearance, or on the other hand may need 

 generations of repetition before becoming fixed. And 

 lastly the changes may be orthogenetic or heterogenetic 

 as to direction, adaptive and accommodative or correla- 

 tive, or wholly inutile as to their functional relations. 



