8 MUTATIVE REVERSIONS IN COTTON. 



degrees in different plantings, even when the seed is of the same stock. 

 Though breeding is undoubtedly a very important factor in reducing 

 diversity, it is no less important to ascertain the relations of environ- 

 ment to the occurrence of reversions. Such differences of behavior 

 are frequently shown by the reversions of the Upland cotton, and the 

 irregular variations of the Egyptian cotton appear to be susceptible 

 to such influences. 



Other forms of reversions, both partial and complete, have showTi 

 relation to differences of environment in experiments with cotton. 

 Ancestral characters that are prominent in one locality may be 

 entirely suppressed in another place where some of the same lot of 

 seed has been planted. Not only the amount or degree of reversion 

 but also the frequency with which particular characters are brought 

 into expression is subject to change through differences of external 

 conditions. The failure of any complete Hindi reversions to appear 

 in the Jannovitch planting of 1908 does not appear merely arbitrary 

 or accidental from the point of view of other experiments, but may be 

 connected with the facts that the seed was sown rather late and that 

 the plants developed under conditions of abundant moisture and heat 

 that have shown a very general tendency to bring the extreme 

 Egyptian characters into expression. Grown under such conditions, 

 plants that are known to be Upland hybrids usually take on the 

 complete Egyptian form and show very few Upland characters — 

 sometimes none at all." 



THE HINDI COTTON CONSIDERED AS A REVERSION. 



Young plants of the Egyptian cotton share the foliage characters of 

 the Hindi, including the reddening of the pulvinus, the wrinkled, 

 swollen cushion where the veins meet, at the base of the leaf. If the 

 Egyptian plants are kept small and stunted by unfavorable conditions 

 the resemblance to the Hindi continues longer, so that plants that 

 finally develop with typical Egyptian characters may be mistaken for 

 Hindi. Late in the season there is another partial approximation 

 of the foliage characters, for the Hindi plants generally lose the red 

 color of the pulvinus that serves as one of the most conspicuous 

 diagnostic features of the Hindi at early maturity and during the 

 preceding stage of growth. The general colors of the leaves are also 

 less distinctive in the latter part of the season, the Egyptian cotton 

 often appearing somewhat lighter and some of the Hindi plants 

 becoming darker. 



Plants that do not show very distinct Hindi features in their habits 

 of growth, leaves, bracts, flowers, or bolls may stiU betray Hindi 



a Suppressed and Intensified Characters in Cotton Hybrids. Bulletin 147, Bureau 

 of Plant Industry, U. S. Dept. of Agriculture, i'JO'J, pp. 17-23. 

 [Cir. 53J 



