506 ANNUAL, EEPOET SMITHSONIAN INSTITUTION, 1908, 



of any movement which will produce higher or better organized 

 types. Accordingly we may assume that their existence as a con- 

 stituent of the flora seems to be doomed to a diminishing importance, 

 if not final extinction. The fernlike plants are also examples of a 

 great phylum of the vegetable kingdom which, in the Carboniferous 

 period, being most suitable for the conditions present, constituted 

 the prevailing type of vegetation, making up perhaps as much as 

 three-fourths of the plant covering of the land. Their organization 

 is one which promises nothing of advantage vegetatively and repro- 

 ductively, and we are now at a time when we see them slowly but 

 inexorably being supplanted by seed-producing forms. 



Of the hypotheses that may be taken more seriously, one that has 

 even lately been regarded with much favor, predicates that organisms 

 undergo transformations, or alterations by adaptive changes in their 

 organs and entailed functions, as a direct reaction to environmental 

 factors, and the altered features becoming fixed and inheritable, the 

 organism receives a lasting imprint from its habitat. Migration to 

 new areas or changed climatic conditions might give opportunity 

 for new stimuli and different reactions which might, or might not, 

 affect those previously made. We need not at this time go into the 

 intricacies of the arguments that cluster about this main thesis or 

 weigh the evidence that is drawn from the presence of useless, ves- 

 tigial, and useful characters in various organisms. 



Popular belief in the influence of environment and the inheritance 

 of acquired characters finds its commonest expression in " that plants 

 have been changed by cultivation." Domesticated races are spoken 

 of as " garden forms " by botanists and horticulturists, with the im- 

 plication that they are specialized types resulting from the effects of 

 tillage. Now, so far as actual cultivation is concerned, this assump- 

 tion is without foundation, since at the present time no evidence 

 exists to show that the farm, garden, or nursery has ever produced 

 alterations which were strictly and continuously inheritable, or were 

 present, except under en vironic conditions similar to those by which 

 the alterations were produced, although vague statements and erron- 

 neous generalizations to the contrary are current. It is true, of course, 

 that structural and physiological changes may be induced in a strain 

 of plants in any generation, which may persist in a share to the 

 second, or even in some degree to a third, but no longer. Some very 

 important operations of the market gardener and the farmer are 

 dependent upon this fact. 



The possibility that permanent changes might be induced is by no 

 means to be denied, and it is a fair subject for investigation. Actual 

 evidence is to be obtained only by observations of breadth under 

 guarded conditions. Until this is at hand all affirmative conclusions 

 can be but inferential and suggestive. 



