PLANT HYBRIDIZATION BEFORE MENDEL 363 



"Cross-breeding, then, is a method of investigating particular cases of 

 evolution one by one, and determining which variations are discontinuous 

 and which are not, which characters are capable of blending to produce 

 a mean form and which are not. It has sometimes been urged against 

 this method of investigation that the results are often conflicting. It has 

 been said that such work will only lead to accumulations of contradictory 

 evidence. It is, however, in this very fact of the variety of results that 

 the great promise of the method lies." (p. 64.) 



From the whole of the above, it appears that to Bateson's mind, 

 at that time, one of the principal purposes of hybridization was 

 to determine in what cases blending occurred, and in v/hat cases 

 characters were discontinuous in their descent, which was the 

 first prerequisite to an actual experiment to determine the facts, 

 and the credit for which, as a prolegomenon, unquestionably be- 

 longs to Bateson alone. 



As illustrations of "discontinuous" inheritance after crossing, 

 Bateson cites the case of the crossing of Matthiola incana^ a hairy 

 species, and its smooth variety, crossed by Trevor Clarke, re- 

 porting the fact observed that : 



"On crossing these two varieties the offspring consisted entirely of com- 

 pletely hoary and completely glabrous individuals, no intermediate being 

 present." (p. 64.) 



The case of Lychnis diurna (hairy), crossed with its glabrous 

 variety by De Vries, is also cited. 



"All of the first generation of cross-breds inherited the hairiness in 

 its complete form : when, however, these plants were crossed again with 

 the smooth form, the result was a mixed progeny, of which some were 

 hairy, and others smooth." (p. 64.) 



A third case was given as that of Biscutella laevigata^ reported 

 from the investigations of Miss E. R. Saunders, one of Bateson's 

 pupils. The species type is a hairy plant of the Alps, with a local 

 variety having the leaf surfaces smooth ; the smooth form is 

 found to occur abundantly with the hairy types, intermediates 

 seldom occurring. 



"The result of artificial cross-breeding went to show that of the young 

 seedlings of mixed parentage some were hairy, some smooth, and a good 

 many intermediate. But as these seedlings grew, the hairy and the smooth 

 retained their original characters, while the intermediate ones gradually 

 became smooth. The transition was not effected by actual loss of hairs, 

 but, after the first few leaves of intermediate character, the leaves subse- 

 quently produced were smooth." (p. 65.) 



Bateson goes on to say : 



