THE AMERICAN BOTANIST 21 



of the true nature and cause of these troubles. Some progres- 

 sive people are striving to obtain plants immune to disease and 

 parasites. Agents of the U. S. Agricultural Department, are 

 ransacking foreign countries in search of immune plants and 

 such native stock as could be utilized in regenerative and 

 crossing experiments with our more or less non-resistant 

 plants, the latter perhaps the outcome of our somewhat irra- 

 tional and too hasty commercialized horticulture. In what does 

 immunity of plants really consist? How does this natural 

 protective principle manifest itself in plant life? Under what 

 particular visible or tangible conditions does this innate 

 protection against disease show itself? There seems to be 

 only one reasonable explanation, namely, that we assume the 

 plant, under certain favorable conditions to be capable of 

 producing its own protective elements; and that these are 

 evidently of a highly subtle nature, for we have not been able 

 to detect them with our most powerful instruments, and are 

 not able to analyse them. The process of producing these 

 protective elements can only be explained by presupposing the 

 production of a specific principle, upon which the assimilation 

 of the plant food depends and which is responsible for the 

 condition known as immunity. Should this be the case, then 

 the solution of the whole problem of immunity would be at 

 hand, and the fruit growers would have to look upon our 

 progressive investigators in this direction as the saviors of 

 horticulture. 



1 have been fortunate enough to come in contact with one 

 of these independent investigators, who for the past ten years 

 has given his spare time to the study of this question. He is 

 in a position to prove that nature does provide plants with 

 protective elements, the production of which depends on cer- 

 tain natural conditions to be furnished. The natural, innate 

 protective elements can only be produced by the plant itself, 

 and cannot be manufactured. A fruit tree provided with these 

 elements becomes so completely immune that you may carry 



