2i 4 POPULAR SCIENCE MONTHLY 



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 environic conditions similar to those by which the alterations 

 were induced, although vague statements and erroneous generalizations to the 

 contrary are current. It it 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. 



So far nothing has been offered which would tend to disprove these 

 conclusions. 



It is by no means intended to maintain that the stream of heredity 

 may not be altered by the action of external agents, and the possibility 

 of having such changes ensue in experimental cultures beckons with 

 alluring finger to the observer. So important do I hold this aspect 

 of the matter, that a series of experiments, yet in progress, were 

 begun previous to the mutation cultures, and these tests have been 

 continued and expanded until one plant is now undergoing culture in 

 INTew York, Jamaica, and in connection with the Desert Laboratory, at 

 sea-level and altitudes of 2,300. 5.000. 6,000 and 8,000 feet, and under 

 conditions widely different from those prevalent in its original habitat. 

 If at the end of the decade, this, or any other of the species under 

 test, shows any transmission of the characters induced by the various 

 localities, the care and work necessary in the experiments will be richly 

 rewarded. In this comment reference is had to factors presented by 

 tillage, or entering into the environment of plants in their native 

 habitats. 



Announcement has been previously made that mutations, breaks, 

 saltations or discontinuous action may be caused in inheritance by 

 forces external to the protoplasts and cells, which are the true bearers 

 of the hereditary characters (see p. 17). 



The technique of the methods by which such changes are induced 

 might be simulated by the action of gaseous emanations, from the soil. 

 radio-action, foreign pollen, or by the stings and incisions of insects, 

 but certainly these possible factors would lie as potent with wild as with 

 cultivated plants, as may be seen in the description of the manner in 

 which such changes have been produced. 



The Method of Pedigree-cultures 

 The importance of pedigree-cultures of plants as a means of tra- 

 cing the course and action of heredity has been notably emphasized by 

 recent investigations, and it will be profitable to go into a detailed 

 statement of the manner in which experiments of this kind are carried 

 out. One of the most striking developments of methods of research 

 in botany has been the continually increasing extent to which taxono- 

 mists are having recourse to observations upon growing material in 

 botanical gardens and experimental grounds. In the determination of 



