THE MUTATIONS OF LYCOPERSICUM. 153 



differ more or less from one another in shades of color, but their 

 valuable qualities appear in the increased solidity or consistence, size 

 and fine flavor of the fruit. Their origination has, in many cases at 

 least, been sudden and fortuitous; and, although their specific char- 

 acters are usually heritable, they are so peculiarly subject to degenera- 

 tion that they hardly possess racial properties. The causes of their 

 origination and extinction appear to be irrelative, and both are inde- 

 pendent of specific plant mutation. Still, as I shall show, a few cases 

 of coincidence of their origin with plant mutation are known; and 

 more or less of common plant variation, and even of dwarfing, have 

 sometimes occurred coincidently. Moreover, all cases of atavic re- 

 version, or degeneration, of fruit varieties from their fine quality have 

 apparently been unaccompanied by any material change in the plants 

 bearing the degenerating fruit. Frequently special reference to those 

 reversions will be made further on, but I will first turn aside for a few 

 more or less theoretical remarks upon the character and manner of 

 origination and extinction of the fruit varieties. 



In the simple cases of origination of the fruit varieties of the 

 tomato, unaccompanied with plant mutation, the change occurs only 

 in the pericarp, which becomes the fruit. Also, when atavic reversion 

 occurs it is only the pericarp, that is, the fruit, which is materially 

 affected; and both kinds of these changes are doubtless of molecular 

 origin in the germ cells. Likewise, in all cases of phylogenetic plant 

 mutation the initial act is molecular, and occurs in the germ cell of 

 each ovule which gives origin to a new plant form.* There is no 

 apparent reason to doubt that the mutative acts which thus respectively 

 produced the two new specific forms from L. esculentum might have 

 occurred without the coincident production of a new fruit variety, but 

 as a matter of fact a new fruit variety of high quality was coincidently 

 produced in each case; and the coming change in both plant and 

 fruit was doubtless initiated in one and the same germ cell. Still, 

 because of the essential difference between plant mutation and fruit 

 variation, I think this pericarpal change was only a varietal coin- 

 cidence, and not an essential part of the phylogenetic process in those 

 cases. Moreover, that change is known to have occurred separately 

 in other cases, and to have resulted only in weakly heritable fruit 

 varieties. 



Known cases of degeneration, and final extinction of fine fruit 

 varieties as such, are somewhat numerous, for their instability is very 

 great, although at least most of them remain true to seed from year 

 to year under favorable conditions. Whether the varieties which have 



* For exhaustive discussions of this and kindred subjects see ' Intra- 

 cellular Pangenesis' by Hugo de Vries. Jena, 1889; and also 'Die Muta- 

 tionstheorie,' vol. 1, by the same author. 



