June 10, 1910] 



SCIENCE 



893 



Mendel to discover the phenomena that 

 bear his name. Practical plant breeders 

 now generally use the plant-to-row or 

 centgener method in comparing the value 

 of selected plants. It is probably due to 

 the non-use of such careful methods that 

 the origin of most cultivated varieties is 

 so obscure. In many cases, a so-called 

 sport or hybrid turns out to be a well- 

 known thing — in all probability the result 

 of a stray seed. This is perhaps unavoid- 

 able, as the business of the seed grower 

 does not readily lend itself to accurate 

 scientific methods. 



Of late years our knowledge concerning 

 hybrids and the behavior of characters in 

 hybrids has increased greatly due to the 

 rediscovery of Mendel's laws and the im- 

 mense amount of splendid investigation 

 which was thus stimulated. No more ad- 

 mirable body of work has ever been done 

 than that of the Mendelists. If it con- 

 tinues as rapidly as it has we may soon 

 expect to know approximately the extent 

 to which hybridizing is a factor in the 

 evolution of our cultivated plants. While 

 the methods of the practical breeder are 

 perhaps necessarily different or at least 

 less accurate than those of the scientific 

 breeder, yet the results of the scientific 

 work are already having profound effect 

 on practical methods. 



Without at aU minimizing the fruitful 

 results and greater promises of Mendelian 

 investigations, the subject of sports is to 

 both the breeder and the evolutionist a 

 matter of far greater moment. Certainly 

 our knowledge concerning sports is far 

 less than that of hybrids. The more en- 

 thusiastic Mendelists have evinced some 

 disposition to deny the existence of 

 "sports" in the commonly accepted 

 sense and would explain them as the re- 

 sult of some previous, even remote, cross. 

 But it is self-evident that hybrids pre- 



suppose the existence of two different 

 things to cross, and sporting is supposed 

 to be one method by which a distinct 

 form more or less suddenly arises. Let 

 us examine carefully the evidence regard- 

 ing "sports." Bud sports, where one 

 branch of a plant is different from the 

 rest, occurring commonly as variations 

 with differently colored flowers, differeat 

 leaves, etc., are well known. There can be 

 no question as to the origin of the sport 

 here, though to be sure the parent plant 

 may be a cross or hybrid. Seed sports 

 are supposed to arise in an analogous 

 manner. The general occurrence of cer- 

 tain types of assumed sports is strong 

 argument in favor of their actuality. 

 Thus, white-fiowered variants are known 

 in practically all plants with normally 

 red or blue flowers; cut-leaved varieties 

 are very common and generally distrib- 

 uted among the plant families; dwarf 

 varieties occur in numerous species, as do 

 smooth varieties in hairy species and 

 vice versa. The logical inference is that 

 the difference is due in each case to the 

 same underlying cause. In some cases the 

 origin of these sports is a matter of defi- 

 nite record, as in the ease of the cut- 

 leaved form of Chelidcmium majus, the 

 globose-podded form of shepherd's purse 

 and others. In the white-flowered form 

 of bleeding heart— its only variant— pre- 

 vious hybridisation seems clearly ex- 

 cluded by the absence of any related form 

 that will cross with it. Many such cases 

 can be enumerated and tend to uphold 

 clearly the gardener's idea of sports. But 

 what are these sports, and how do they 

 arise? Apart from the fundamental idea 

 that they are large and permanent varia- 

 tions, breeders and gardeners in general 

 attach three other ideas, namely, that high 

 nutrition and other extreme conditions 

 favor sporting; that many plants must be 



