EVOLUTION OF PARASITIC FUNGI. 117 



■spores from the barberry which Avere developed from the oat 

 group woukl not work on the rye group, Avhile they would work 

 on any member of the oat group. 



Similar form species were found in the case of several other 

 Uredinese which were investigated, and it would not be surpris- 

 ing if similar specialized forms of species were to be found 

 throughout the entire range of the more strictly obligate para- 

 sitic fungi. 



Problems. — These are some of the tendencies which I be- 

 lieve are manifested in a greater or lesser degree in the evolution 

 of species among parasitic fungi. It must be admitted that in 

 many instances we have indulged largely in speculation, but 

 there is, I think, reasonable ground for speculative discussion 

 •upon these tendencies. We might regard them as to some extent 

 hypothetical, and thus they would serve to indicate some of the 

 lines on which investigation might profitably be carried further 

 on, for the solution of these questions would throw a great deal 

 of light on the treatment which should be given or recommended 

 for the prevention of the fungous diseases of many of our culti- 

 vated plants. 



A number of the problems connected with the subject are 

 suggested in the discussion of the various paragraphs, and the 

 solution of these questions requires not only the investigations 

 of the mycologist, but also of the practical fruit grower. Prophy- 

 lactic treatment, no doubt, must be depended on in a great many 

 cases ; but in many others by careful attention to the breeding of 

 healthy, stocky, and resistant varieties of fruits and other plants, 

 to this extent we shall be able to dispense with the knapsack 

 sprayer. 



The number of varieties noted for productiveness and for 

 fruiting at opportune seasons is one of the wonderful achieve- 

 ments of the horticulturist and florist. While hardiness is also 

 a characteristic of some of the new productions, it would seem 

 that less attention had been given to this very important quality 

 in planthood than to other points. One of the important prob- 

 lems is the development and fixing of disease-resistant varieties, 

 as well as the general well-being of plant life, and the setting of 

 a wholesome environment to counteract the tendencies among 

 plant enemies which the absence of these qualifications in 

 plant culture is promoting. 



