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TEXTBOOK OF BOTANY 



When the poHination of plants which are naturally open pollinated is 

 controlled so that only selfing can occur, several different kinds of 

 progeny are obtained from the same parent. That is, the plant does not 

 "breed true." It is a hybrid, and its mixed parentage becomes evident in 

 its progeny (Fig. 203). But if each individual in its progeny is selfed, 

 and if this process of selfing is repeated in all individuals for several 

 successive generations, several different kinds of plants are eventually ob- 



FiG. 203. Hybrid segregation in corn. Photo by G. W. Blaydes. 



tained, each of whose progeny appears uniform when growing in a 

 similar environment. In this way several inbred lines of plants are 

 obtained from the original hybrid parent.^ Further inbreeding results 

 only in a continuation of uniformity in the progeny of each inbred line. 

 Inbred plants are pure-line plants with respect to many of their char- 

 acters. In contrast to hybrids, pure-line plants continue to breed true. 

 Plants that naturally have only close pollination are natural inbred and 

 pure-line plants. 



Pure-line plants of some species, such as those of corn, may be less 

 desirable than the hvbrid varieties obtained by cross-pollination because 

 they are smaller, less vigorous, or more susceptible to parasites, or have 

 fewer seeds and fruits than the hybrids. More desirable and uniform 

 hybrids may be obtained by restricting cross-pollination to certain se- 



^ Probably more than 2000 inbred hnes of corn liave been obtained by this method, 

 and sexeral hundred of them have been used as a basis of securing better N-arieties of 

 hybrid corn. Some of the inbred hnes of corn are albinos and perish in the seedling stage. 

 Certain others also fail to grow to maturity and reproduce. 



