80 



CROSSING. 



In another chapter, the question whether any considerable 

 group of domestic species can originate from one single domest- 

 icated one, will be more fully discussed. 



In garden plants, there exist a number of aberrations from 

 normal colour and normal shape, which frequently recur in the 

 most diverse groups. Partial and complete loss of pigmentation 

 laciniations, doubleness of flowers are characters which are 

 found in varieties of the most diverse cultivated plants, and 

 which are found to breed true in domestic species. Mutation 

 seems at the first view to be the most probable cause of the 

 production of these novelties, but the example of the rats 

 should make us cautious. Is it not possible that such new char- 

 acters have resulted from crossing, from re-combinations of 

 genes such as they were present and absent in the genotype 

 of two or more species or even sub-species? 



Erwin Baur's work with snap-dragons furnishes a good many 

 instances of the origin of wholly new characters in second and 

 later generations of species-crosses. In the F 2 of a cross be- 

 tween Antirrhinum majus and A. molle, Baur obtained a great 

 number of novelties. Among these, the greatest number were 

 what the Weismannians would call re-combinations of parental 



characters, but several plants 

 showed qualities which are 

 wholly new, not only for the 

 two species crossed, but for 

 the whole genus Antirrhi- 

 num. Among other things, 

 / ^ A~ plants were produced with 



POX f Ag. peculiar appendages, fringes. 

 Vj \to* Other plants from species 

 hybrids produced branches 

 of wholly female flowers 

 without petals standing in 

 the place of the flowers. 

 The seed-firm of Haage and Schmidt in Erfurt crossed mari- 

 golds, Dimorphocotheca aurantiaca and Calendula pluviatilis. 



Fig. 10. 



Variability in the F2 of an Antir- 

 rhinum cross, after Baur. 



