abstracts: genetics 199 



Agricultural exploration and introduction work is an important 

 function of the Government, but the time seems to be approaching 

 when these explorations should be back-grounded by phytopathological 

 surveys or the explorations and phytopathological work done simul- 

 taneously. Theoretically plants should be free from diseases and in- 

 sects, and, although theoretically only, there is no reason why efforts 

 should not be made to approach the ideal conditions in this respect. 



The development of some phases of plant hygiene will require com- 

 bined effort and coordinated action of pathologists and others. Syste- 

 matic world-wide studies of the botanical relationships of some of our 

 principal crops seem desirable, not only to obtain a foundation for 

 intelligent action regarding the economic use of plants, but to aid 

 in supplying material with which to fight our present plant enemies. 



The gradual shifting of plant industries from one region to another 

 is also an interesting study and is due in many cases to lack of proper 

 appreciation or understanding of plant sanitation. Sanitation as 

 a phase of hygiene must be considered. The removal of many causes 

 of disease is practicable, but a vast amount of educational work must 

 be done in this field before effective action can be secured. The in- 

 dividual can accomplish much, but only through the vState can far- 

 reaching results be brought about. The State, however, is moved 

 in such matters only by a groundswell of public opinion, and the best 

 way to create a groundswell for plant sanitation is to bring the individual 

 grower to a realization of its importance in all phases of his work. 



B. T. G. 



GENETICS. — A study of hybrids in Egyptian cotton. Thomas J. 

 Kearney and Walton G. Wells. Amer. Nat. 52 : 491-506. 

 Oct.-Nov., 1918. 



Hybrids were made between two varieties of Egyptian cotton, Pima 

 and Gila, both of which had presumably originated by mutation. The 

 two varieties, as represented by the progenies grown from selfed seed 

 of the individuals which were the parents of the hybrids, differed sig- 

 nificantly in their means for some two dozen characters. Most of these 

 are size or shape characters. The parental ranges for nearly all charac- 

 ters overlapped considerably. 



With very few exceptions, the means of the simple intervarietal 

 hybrids, in the first, second, and third generations, fell between the 

 parental means. The ^/s backcrosses obtained by twice crossing the 



