342 THE POPULAR SCIENCE MONTHLY 
THE ROLE OF HYBRIDIZATION IN PLANT BREEDING? 
By Prorgessor BE. M. BAST 
HARVARD UNIVERSITY 
(ger word hybridization has been used with many meanings. The 
term is used here to denote the crossing of any two plants that 
differ from each other in a heritable character, whether they are of the 
same or of different species. 
There is intimate connection between the réle of hybridization and 
the réle played by selection. It comes about in this way. Inherited 
variations are produced by nature with considerable profusion. New 
characters appear and old characters are lost: these form the working 
basis of selection. But whether they are large or small they are usually 
inherited completely. They are the units of heredity; or, if they 
are sometimes transmitted in units of lesser degree, they may be 
compared to chemical radicals. 
The main object of hybridization then is the shuffling of these units 
in the first hybrid generation and their recombination in the next 
generation. There are, however, various phenomena attending hybridi- 
zation, and J will endeavor to illustrate the following as those of most 
importance: (a) Recombination of characters and their fixation, (b) 
production of desirable combinations in the first hybrid generation and 
their continuation by asexual propagation, (c) production of fixed first 
generation hybrids, (d) production of blends. 
If we begin at the real beginning in this discussion, we must say @ 
few words concerning the actual mechanical operations of crossing. 
The first foundation stone to be laid is a knowledge of the flowering 
habits and flower structure of the plants to be used. Of course a careful 
examination of the flowers will show the easiest and surest method of 
removing the stamens of the flowers that are to be pollinated and of 
protecting them from foreign pollen. What is not so easily determined 
are the precise conditions under which the cross should be made to be 
successful. The proper preparation of the breeding plot even before 
the plants are grown is necessary. One takes it for granted that some 
fertilizer will be used, for the plants must be normal to seed well. The 
three essential elements of soil fertility are nitrogen, potassium and 
phosphorus, and to get the best results compounds of these elements 
must be present in proper proportions. First, available potash must be 
1This paper is based on one of a series of popular lectures delivered at the 
Bussey Institution of Harvard University, April and May, 1910. 
