HYBRIDISATION 331 



however, it was observed that in most fields a few plants were not 

 affected by the disease, while the destruction was otherwise universal. 

 Seed of such individual plants was saved and sown in rows between 

 ordinary seed and on soil known to be badly infected. Any plants 

 within the special rows that subsequently manifested the disease 

 were uprooted. Seed was again preserved and similarly treated till 

 it had been satisfactorily proved that a stock had been thus discovered 

 that was to all intents and purposes Wilt-resistant. But an interest- 

 ing fact has now to be added : namely, that in thus selecting for ' Wilt- 

 resistance ' it was observed that the special properties for which the stocks, 

 plants had been previously grown were by no means lost, in fact in 

 some cases they had been improved. But by far the most important 

 fact demonstrated was that, in the case of the ' Sensation Sea Island 

 Cotton,' even in the seventh generation, the Wilt-resistance was as 

 marked as when originally discovered. Thus by simple selection of 

 the fittest the complete victory of ' Wilt ' had been attained. 



The explanation of this marvellous and highly satisfactory 

 resistance of infection, thus manifested by individual plants, has not 

 as yet been satisfactorily explained, but it appears to be physiological 

 rather than mechanical. There are no structural manifestations as 

 yet recorded by which a resistant plant can be recognised. Further, 

 it may be reiterated that the fully resistant types mentioned appeared 

 as isolated individuals and bred true at once. Selection toward the 

 production or even the strengthening of the special property was not 

 required. Eesistance was fully established from the beginning. It 

 was therefore a manifestation of the ' mutations ' of De Vries, rather 

 than of the ' slight variations ' of Darwin. 



There can be no possible doubt, however, that the systematic Value of 

 selection of stock for each individual plantation (or restricted area of 

 plantations) is not only imperatively necessary, to preserve and 

 maintain the quality of the stock, but is the chief method of 

 improvement to the conditions of soil, climate and methods of 

 cultivation, available to the ordinary cultivator. Nothing could be 

 more disastrous than the use of seed promiscuously that is to say, 

 in utter disregard of both the plant and its environment. 



Hybridisation and Crossing of Stock. Much difference of opinion Hybridisa- 

 exists among experts as to the value of this process of cotton 

 improvement. Dr. Angelo Aliotta, in his ' Eiv. Grit, del Genere 

 Gossypium,' 1903, gives an elaborate statement of the races of 

 cultivated cottons which he thinks have been produced through the 



