50 HORTICULTURAL SOCIETY OF NEW YORK. 



culty in obtaining wilt resistant selections of the watermelon, because re- 

 sistant individuals are less numerous; but several strains are now being 

 grown which promise to retain this quality. Selections were made this year 

 from resistant vines which remained healthy on land where all melons had 

 been killed for four years previous. Our hopes are further stimulated by 

 the fact that the citron and an African melon, both forms of Citrullus vul- 

 garis, are resistant to wilt. Hybrids between, these and our better watermelons 

 have been made, and they promise to be wilt resistant, though it is not yet 

 known whether an edible product can be obtained. This work is now being 



continued. 



Discussion of ^Methods and Results. 



The question of the reason for the marked resistance to infection by 

 wilt fungi noted in individual plants of cotton, cowpeas and watermelons has 

 not been satisfactorily answered. Our own observations lead us to believe 

 that it is not due to any mechanical protection afforded by thicker cell walls 

 or in similar ways, but that it probably is due to some physiological reaction 

 within the plant, possibly connected with the presence or absence of certain 

 enzymes. This interesting problem has not yet been fully worked out. It is 

 certain that resistance to one disease does not necessarily imply any immunity 

 against others. One of the wilt resistant cottons, for instance, is very much 

 affected by the angular leaf spot. 



The important points that concern the plant breeder are that individual 

 plants do occur which resist these wilt diseases, and that their descendants 

 inherit this resistance. The determination of the proper methods to pursue 

 in utilizing these variations and fixing them into stable varieties has been the 

 object of some of our investigations. The final conclusions can hardly be 

 drawn as yet. They will probably be found to confirm principles already 

 known to plant breeders. 



Importance of the Individual. 



The most important point that has been brought out is that in seeking a 

 disease resistant variety the attention must be directed to the selection of re- 

 sistant indk'iduals to use as the parents of a new strain, rather than to the 

 discovery of the desired characters in a variety already existing. There is no 

 question, of course, that varieties differ in their susceptibility to disease, and 

 a thorough test of a large number of varieties in a location where they will 

 be exposed to the disease against which resistance is desired would be the 

 first step in a system of plant breeding. But if even the best variety is not 

 entirely resistant, the selection from it of individual plants that have the de- 

 sired character may lead to the production of a resistant strain. 



Furthermore, it is very desirable to save the seed from each plant sep- 

 aratelj', tiiat is, to take as the basis of each selection a single exceptional in- 

 dividual, rather than to mix the seeds of a number of good plants. The rea- 

 sons for this are, first, that it insures greater uniformity than can be had 

 from seed of mixed parentage, which is especially desirable in breeding cot- 

 ton; and second, that if any selection lacks prepotency or shows other un- 

 desirable characters, it can be wholly discarded in the second generation, 

 while in mixed lots this could not be done; third, opportunity may be had 

 for exact studies on heredity. If the aim is to produce a select variety too 



