The Development and Properties of Raw Cotton pp. 63-64 (1915)
William Lawrence Balls

Fertilization

Of the many pollen-tubes which germinate on the style, only some twenty or so can find an ovule. Those which were too late in starting, or too slow in growing down the style, also perish, and their remains may partly be traced in the walls of the young fruits; while the rest are thrown off when the style breaks away from the point of the young boll.

Some remarkable features of this race between the pollen-tubes require further study. The style of some kinds of cotton is either non-nutritious, or more probably poisonous, to the pollen of other kinds. Thus, crosses between the Indian group of cottons and the Upland or Peruvian groups do not appear to be possible. Uplands and Peruvians can, on the other hand, be artificially intercrossed with ease. Even in this case, however, if equal amounts of self and foreign pollen are placed on the style simultaneously, so that both have an equal chance, 97 per cent. of the victors will be self-tubes; so that, although Egyptian pollen can grow down an Upland style quite satisfactorily, it cannot grow so fast as the Upland's own pollen can do, and vice versa. If, lastly, the pollen mixture is made with pollen from the first cross between Upland and Egyptian, the percentage of wins credited to the home team falls to about 60 per cent.; the hybrid pollen is said to be more "prepotent." These facts have considerable economic bearing on the possibility of keeping cotton strains pure with fewer precautions, but it will take a great deal of tedious research to find whether they have any utility.

Cotton Bibliography

Pollen Mixtures