December 8, 1906 



horticulture: 



617 



Atavism or Revertion 



'Th-is combination > 

 and varieties ■ 

 in the uear 19C 



Bateson says, "It is a curious 

 and unexplained fact — constituting 

 one of the most fertile fields of 

 inquiry — that when dissimilar garn- 

 ets meet they should so often pro- 

 duce an ancient form. That is wliat 

 we now recognize as the rationale 

 of Darwin's Eevertions on Cross- 

 ing." When Dar-n-in crossed his 

 pigeons he brought back an old 

 form ; and so in crossing many 

 plants you can get back a reversion- 

 ary form by uniting two dissimilar 

 gamets. 



Hugo de Vries says, "Crossing is 

 a means of analyzing compound 

 characters." It is also a means 

 of combining the elements of such 

 characters, and of building up the 

 original type out of its components. 

 In some cases the compound nature 

 of a character may be evident, in 

 others it is not, and in most cases it 

 is as yet doubtful. So it is clear 

 that a combination gained by cross- 

 ing may assume the aspect of some- 

 thing quite new, and this wiU be 

 nearly always the case where it is 

 not possible to discern the exact 

 relation of the "new" character to 

 those of the parents used for the cross. If now this 

 "new" character happens to have been present in some 

 of the ancestors of the crossed types it will resemble 

 a reversion to this lost feature, and provided no other 

 explanation offers itself, it will easily be taken for 

 an example of atavism. Looking at this infer- 

 ence from another point of view, we are led to 

 suppose that perhaps many cases registered now 

 as atavism caused by crossing, may probably originate 

 in this way. In other words we may expect in all 

 cases, where a compound character has been lost in the 

 course of evolution, but where its components still exist 

 in separate species or varieties, that it will be possible 

 to rebuild the old characters by combining the partial 

 ones by means of crossing. Such a combination would 

 evidently deserve the title of artificial atavism. The 

 writer has produced or caused by hybridizing a clean 

 cut reversion. It will be seen that the accompanying 

 diagram is composed of three different species, viz., Vitis 

 Labrusca, V. riparia and Y. vinifera. It will also be 

 seen that there is much less of V. riparia in the combi- 

 nation than of Labrusca and about the same as that of 

 vinifera, but notwithstanding that fact, the crossing of 

 "Mammoth Cluster" with "Old Gold" has produced or 

 reproduced, to all appearance a complete riparia grape. 

 Mammoth Cluster is a staminate vine and Old Gold is a 



onipleted 

 J.WKUe 



L. Vitis Labrusca 

 V.Vitis Vinifera 

 R.Vitis Riparia 



pistikte and self sterile, a very sweet white grape and 

 blossoms some two weeks later than the riparia, so 

 there was no possible chance for it to have been pol- 

 lenated from a riparia vine ; it will be seen by referring 

 to the diagram that the riparia is found among the 

 ancestors of both Mammoth Cluster and Old Gold. It 

 is probable that two gamets possessing the blood or 

 potentialities of the riparia united and produced the 

 reversion. But if heredity is as Luther Burbank and 

 Prof. Emil P. Sandstcin regard it, such an occurrence 

 could hardly take place. According to Burbank, 

 "Heredity may be said to be the sum of all the effects of 

 all the environments of all past generations on the 

 responsive ever moving life forces, or in other words, a 

 record kept by the vital principle of the struggle onward 

 and upward from simpler forms, not vague in any 

 respect, but indelibly fixed by repetition." 



Prof. Sandstein says, "Thus the individual animal 

 or plant contains potentially the sum total of all the 

 ancestral hereditary characteristics of the variety or 

 species, regardless of the number of ancestors." 



I can hardly conceive of such statements being true. 

 If I take a cross section from the trunk of a tree, the 

 rings of yearly growth will be a good record of the 

 seasons in which the growth was made ; the broad circles 

 will indicate that the season in which the growth was 



