12 BULLETIN 1111, U. S. DEPARTMENT OF AGRICULTURE. 
Improvement of varieties was more feasible under the old system of 
private gins, because the careful planter could maintain uniform 
strains of cotton by selecting the best individual plants, isolating their 
progenies, keeping the seed separate, and furnishing pure seed to 
stock other plantations, as the custom was. With selection practiced 
and superior stocks isolated, the old plantations had the advantages of 
one- variety communities, while under the public-gin system varieties 
are mongrelized and destroyed, even before they can be established 
widely in cultivation. 
The cotton industry should have been placed on a community basis 
when public gins supplanted the former system of private or planta- 
tion gins after the Civil War, but methods changed gradually and 
consequences were not considered. Mechanical improvements and 
economic advantages were reckoned, but not the effect upon seed sup- 
plies. Ginning is done with less labor by the modern high-power 
equipment, but the public-gin system has made it very difficult to 
keep seed pure or to have superior varieties in general cultivation. 
According to the general testimony of the cotton trade there has 
been a serious deterioration in the quality of the American cotton 
crop in the half century since the Civil War period, and this can be 
understood when account is taken of the effects of mixing and cross- 
ing different varieties and the general use of ordinary " gin-run " 
seed for planting. The system of plantation gins survived longer 
in the Sea Island districts of the Southeastern States and in the Mis- 
sissippi Valley, where long-staple Upland varieties were grown, so 
that the long-staple branches of the industry remained on a somewhat 
better footing until recent years. But with the boll-weevil invasion 
the dominance of the public-gin system and of mixed short-staple 
varieties became complete. 
Everybody who knows the construction of cotton gins is aware that 
the mixing of seed must take place between successive lots that pass 
through. The gin construction is such that all the seed does not pass 
out of the machinery when the ginning of a bale is completed. If the 
machinery is not thoroughly cleaned, which requires time and effort 
and very seldom is done, some of the seed from one lot of cotton is 
held over and passes into the next lot, so that the seed stock is con- 
taminated if the two lots represent different varieties. Though the 
fact of gin mixing could not be doubted, the nature and extent of 
the process were not definitely known until 1915, when a method 
of demonstration was devised by Dr. D. A. Saunders, at that time 
in charge of the cotton-breeding station of the United States Depart- 
ment of Agriculture, at Greenville, Tex. The expedient used by 
Doctor Saunders was to color the seeds that were left behind in the . 
gin after a bale had been finished in the usual manner. After the 
seeds had been dyed red and were thoroughly dry they were put back 
