November 29, 1901„] 



SCIENCE. 



843 



herein described originated by spontaneous, 

 saltatory mutation, without cross- fertiliza- 

 tion, and that this form of mutation difiers 

 only in degree, not in kind, from the salta- 

 tory origin of new species which has been 

 elaborately described and demonstrated by 

 Professor de Vrles in his work already re- 

 ferred to. 



This manner of origination of the Wash- 

 ington variety of tomato is assumed for the 

 following reasons: (1) No probable source 

 of cross fertilization was discovered by care- 

 ful investigation ; (2) all the new plants 

 were identical with one another in their 

 varietal character ; and (3) the mutation in 

 question was exactly repeated in a succeed- 

 ing crop under like conditions of isolation 

 and cultivation. If my Acme plants had 

 received adventitious fertilization by pollen 

 from any other than flowers of their con- 

 nate crop-associates, the cross- fertilization 

 would doubtless have been incomplete as 

 to the whole crop and various as to the 

 kinds of hybrids produced. Even if it were 

 credible that the first case of complete mu- 

 tation of my whole crop might have been 

 the result of cross fertilization from some 

 unknown source, it would still be too much 

 to believe that exactly the same result could 

 have been produced a second time in suc- 

 ceeding years by such adventitious means. 



Saltatory mutation may be said to have 

 both a predisposing and an exciting cause, 

 the former being always present, at least 

 latently, and the latter acting only under 

 the stimulation of changed conditions ; but 

 I do not propose to discuss the nature of 

 either of them. While the exciting cause 

 of saltatory mutation in plants very often 

 acts in connection with the process of cross- 

 fertilization, it sometimes, as has been 

 shown, acts independently of it. In such 

 cases as that which is here recorded one 

 naturally seeks the exciting cause in some 

 peculiarity of the physical conditions under 

 which the plants grew. I by no means as- 



sume that the exciting cause of the muta- 

 tion which produced the Washington va- 

 riety of tomato will be found in the physical 

 conditions of my garden and its vicinity, 

 but the following mention is made of those 

 conditions, that they may be considered in 

 any inquiry that may be made concerning 

 it. My ground is in a northern suburb of 

 Washington and, before the Civil War, it 

 was part of a worn-out farm of stiiT clayey 

 soil. It is somewhat dry, but was watered 

 freely with Potomac river water, especially 

 during the hot summer months. It was 

 fertilized with stable manure, lawn-mow- 

 ings (used also as mulching) and crude 

 sodium nitrate, the last about half an ounce 

 to the plant, applied in weak solution near 

 the roots. Besides the evident obscurity 

 of the exciting cause of the case of muta- 

 tion in question, when considered with, as 

 well as aside from, reference to these con- 

 ditions, it should also be mentioned that no 

 similar case has been reported from other 

 gardens around Washington in which to- 

 matoes are grown, although practically the 

 same conditions prevail in many of them 

 that exist in mine. 



That the mutation which produced my 

 new Washington variety was not atavic, or 

 retrograde, in character is shown by the 

 horticulturally improved characteristics of 

 the fruit, and by the fact that the entire 

 habitus of the plant is unlike that of the 

 parent Acme, and also unlike that of the 

 plants from which the Acme was originally 

 produced. In both fruit and habitus the 

 new variety is also very unlike those com- 

 mon tomato plants and fruit to which all im- 

 proved varieties sooner or later convergently 

 revert under promiscuous cross-fertilization 

 and careless cultivation. Although the 

 Acme is one of the least unstable of the 

 very many varieties of tomato which gar- 

 deners have recognized, its deterioration 

 by atavic reversion is very common and is 

 readily observable in the markets of Wash- 



