208 THE SMALL GRAINS 



shows a great degree of self-pollination. Two isolated 

 spikes on different plants inclosed with each other are 

 much more fully fertile, and it seems certain that every 

 variety of rye must depend upon cross-pollination between 

 different plants for normal fecundation and grain pro- 

 duction. Since rye is necessarily cross-fertilized, 'it is 

 difficult to separate and establish distinct commercial 

 varieties. Even when such varieties are established, 

 the difficulty of maintaining them pure is great and 

 probably demands concerted community action. The 

 difficulty is increased in direct proportion to the size of 

 neighboring fields of rye. On the other hand, the fact 

 that color of seed is a dependable segregating character 

 will assist greatly in maintaining purity of strain, as the 

 results of crossing may be at once detected in the kernels. 

 217. Mendel's law of hybridization. In 1865 Gregor 

 Johann Mendel published an article on plant hybrids in 

 the Proceedings of the Natural History Society of Briinn, 

 Austria, in which he discussed fundamental principles of 

 hybridization and heredity. 1 This paper appears to have 

 remained unknown for 35 years. In 1900, De Vries, in 

 searching plant-breeding literature, came across the 

 paper and published an account of it that year. After- 

 ward, Correns, Tschermak, Bateson, and others dis- 

 cussed the theory of Mendel in various papers. Webber 

 introduced the subject in this country, while Spillman 

 found numerical results in his own study of wheat hybrids, 

 corresponding to those reported by Mendel, before the 

 latter's views were republished. 2 The published restate- 



1 There is an English translation of the paper in the Jour. R. 

 Hort. Soc. XXVI, 1910. 



2 An interesting statement of the rediscovery of Mendel's Law 

 is given in Bailey and Gilbert, Plant-Breeding, pp. 155-156n 



