234 THE PLANT WORLD. 



Catalina Mountains in Arizona. During this dissemination it 

 las substituted radisli-like structures for the bunch of fibrous 

 roots characteristic of it, and developed new forms of leaves and 

 stems, while throughout it shows tissues and arrangements of 

 tissues wholly unfamiliar to it; all of which has been brought 

 about with comparative rapidity in five years. On the other 

 hand, Lysimacliia tcrrestris has been transferred from a terres- 

 trial habitat to an aquatic, with similar sweeping changed by way 

 of accommodation in even a briefer period. 



So important are the possible results in this phase of experi- 

 mentation held to be that the Department of Botanical Research 

 of the Carnegie Institution of "Washington has established plan- 

 tations, under permits from the management of the National 

 Forest, at 8,000 feet, in a moist alpine climate, and at 6,000 feet 

 in an arid situation in the Santa Catalina Mountains, in connec- 

 tion with a small experimental farm, at 2,200 feet in the alluvial 

 irrigated soil of the Santa Cruz vallev near Tucson. Without 

 going into detail at this time it may be stated in general that the 

 experimental work carried on at these plantations involves an in- 

 terchange of plants among the three stations, and also introduc- 

 tions from various locations in different parts of the world. In 

 the two seasons that have elapsed since organized, ample reward 

 has been obtained for the effort expended. 



The methods and the results discussed above refer wholly 

 to adaptive or responsive changes made by the bodies of plants 

 subjected to any given environment, and forming accommoda- 

 tions to it. These alterations are of the greatest importance in 

 the extension of the range of any plant, and by a study of them 

 the accommodation response may excite the plant to increase the 

 very feature of its structure of e<?onomic importance, and sup- 

 press those useless or harmful in its application to our needs. 



Still a last possibility is to be taken into account in the 



great changes to which plants are subjected in acclimatization 



work. I have recently demonstrated that external agencies may 



be made to act upon the germ cells of plants in such manner that 



'Changes take place which are expressed in the progeny, and are 



