b MUTATIVE EEVEESIONS IN COTTON. 



our domesticated plants. It is a mistake to think of natural species 

 as uniform groups of plants that show only one set of characters, 

 like our carefully selected varieties. Very few of our cultivated 

 plants have so many wild or unimproved relatives as does the cotton, 

 to serve as a basis of judgment, regarding ancestral diversities and 

 reversions. 



RELATION OF REVERSION TO COHERENCE OF CHARACTERS. 



Complete reversions may be considered as related to a phenomenon 

 already described as coherence of characters.'' In cotton hybrids 

 there is a general tendency for the characters derived from the same 

 ancestor to come into expression in groups or combinations. It sel- 

 dom or never happens that a single character of one ancestor comes 

 into full expression in a hybrid; that is, without being accompanied 

 by the expression of other characters of the same parent. Coherence 

 of characters appears to have a phj^siological significance. Among 

 the hybrid plants that are superior to the parent stocks in vigor, fer- 

 tility, and quality of lint, characters of both of the parental types are 

 brought into expression in coherent groups. Hybrids that bring the 

 characters of only one parent to full expression are not superior, 

 while those that show incongruous combinations of characters are 

 notabl}^ deficient in fertility. A notable example of this relation 

 appeared in a field of Jannovitch cotton raised from imported seed at 

 Somerton, Ariz., in 1909. The plant had the habit of growth, leaves, 

 and bracts of the Egyptian cotton, but changed suddenly to Hindi 

 characters in the long-toothed calyx, white flowers, and broadly conic 

 light-green bolls. At the same time it retained the Egyptian charac- 

 ters of short stamens and long exserted stigmas. Though having 

 great vegetative vigor, this plant was quite sterile. The anthers con- 

 tained pollen, but did not open to shed it. The stigmas were abun- 

 dantly cross-pollinated by insects, but no ovules developed and not 

 a single boll matured. *" 



VARIATIONS OF DIVERSITY IN THE SAME STOCKS. 



The fact that plants with a preponderance of Egyptian ancestry, 

 such as three-quarters or upward, may show little or no sign of Upland 

 admixture accords with the general tendency toward coherence in 



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

 of Plant Industry, U. S. Dept. of Agriculture, 1909, p. 16. 



f> The empty carpels of this plant showed a further peculiarity nofehitherto observed. 

 The ridge that marks the middle of the wall of the carpel, the line of dehiscence of the 

 ripe fruit, gave rise to a series of long slender hairs that projected into the cavity. 

 Hairs of the same kind were found afterwards in normal plants and may be looked 

 upon as an additional storm-proof character, since they undoubtedly help to hold the 

 lint and seeds in place after the carpels have opened. 

 [Cir. o3] 



