Kearney: A Plant Industry Based upon Mutation 



61 



and seed mixture. Consequently the 

 maintenance of the Egyptian type of 

 cotton has until recently depended upon 

 the successive appearance of desirable 

 mutants which have given rise to new 

 varieties. 



It is a noteworthy fact that mutation 

 in Egyptian cotton is associated with 

 lack of purity in the parent stock. From 

 the Mit Afifi, which, like all varieties 

 grown in Egypt, has become a congeries 

 of biotypes, the parents of several well- 

 marked varieties have been selected in 

 Egypt and in Arizona. Similarly the 

 Yuma variety offers numerous heritable 

 variations and has given rise to one ver}^ 

 distinct new variety, the Pima. On 

 the other hand in the Pima variety, 

 which has been protected from cross- 

 pollination with other stocks, no con- 

 spicuous mutant has yet been detected. 

 Nor have mutants been found in such 

 stocks of the Yuma, Gila and Sakellar- 

 ides varieties as have been line-bred. 



While mutation in Egyptian cotton 

 has been observed only in heterozygous 

 stocks, the origin of such extreme mu- 



tants as Yuma and Pima can scarcely 

 be explained by the recombination hypo- 

 thesis. Comparison of the parent stock 

 with any other with which it could have 

 had recent opportunity to hybridize did 

 not reveal the source of the distinguish- 

 ing characters of the mutant. Further- 

 more, the absence or extreme rarity of 

 forms intermediate between parental 

 type and mutant does not accord with 

 the current conception of recombination. 

 It will be asked whether the origin of 

 varieties in other types of cotton is like- 

 wise due to mutation. How, for exam- 

 ple, have the almost innumerable 

 varieties of American Upland cotton 

 come into existence ? The data at hand 

 do not allow of a positive answer to this 

 question, although it seems to be fairly 

 well established that many of the 

 Upland varieties have been derived 

 from single-plant selections. The pre- 

 sumption that these plants were mutants 

 is not a far-fetched one, since it would 

 seem improbable that Egyptian is the 

 only type of cotton which is in a mutat- 

 ing condition. 



Why the Button-Ball Degenerates in Towns 



To the Editor of Journal of Heredity: 



I have followed with much interest 

 your articles on Platanus. I am 

 tempted to write this letter by a question 

 in vour issue of December, 1917, page 

 553. 



Prof. Augustine Henry, Royal College 

 of Science for Ireland, Dublin, asks: 



"Can anyone explain how the native 

 species of Platanus is inferior to the im- 

 ported one, and why the latter is pre- 

 ferred? How the former degenerates 

 when planted in American towns?" 



The native species, Platanus occiden- 

 talism requires a rich, deep and somewhat 

 sandy soil in which it grows to great 

 size. I have seen trees from 4 to 5 feet 

 in diameter growing along the streams 



in eastern Kansas. Some that were 

 reduced to saw logs proved to be sound 

 to the core. When planted on the 

 heavy soil of uplands, or in towns where 

 stones, brick-bats, ashes and other 

 similar material are mixed with the 

 already poor soil, the species has a very 

 hard time of it and is generally sickly 

 and short-lived. 



Platanus orientalis is naturally more 

 vigorous and of quicker growth-; it does 

 not object to the heavy soils, excepting 

 when there is too much alkali present. 



This has been my experience during 

 many years of close observation. 

 Yours verv sincerely, 



E." F. A. Reinisch, 



Supt. of Parks, 

 Topeka, Kans. 



