154 POPULAR SCIENCE MONTHLY. 



arisen from the two new specific plant forms that were derived by 

 mutation from L. esculentum are more permanent than are those of 

 the mother species I do not now know, but all the cases of atavic 

 reversion known to me have occurred with fruit varieties of the mother 

 species. It therefore seems possible that the fruit varieties arising 

 from L. solanopsis and L. latifoliatum may be less liable to hybridity, 

 or otherwise more permanently heritable, than are those arising from 

 the mother species, L. esculentum. The fruit of the two derived 

 species has always been of fine quality and, for them, intraspecific fruit 

 reversion would not be degeneration; but the original fruit of the 

 mother species was very inferior, and any reversion of its improved 

 quality would be degeneration. For those who may have the oppor- 

 tunity, it will be interesting to observe the relative permanence of the 

 fruit varieties arising from the different species, and the course that 

 may be taken in any qualitative changes that may occur in the fine 

 fruit varieties of the two derived species. In the case of the mother 

 species the trend of fruit degeneration is direct, intraspecific and 

 towards the primitive fruit condition. If similar reversional trend 

 in the fruit of the two derived species could occur it would necessarily 

 be accompanied by coincident reversion of specific plant characters, an 

 occurrence which I think improbable, or we should have one and the 

 same kind of degraded fruit borne by different species. 



Eeturning to the practical consideration of atavic reversions of 

 fine fruit varieties, it may first be mentioned that they often occur 

 locally and affect only a few plants, or the crop of a single garden 

 or field, the variety thus affected remaining unchanged elsewhere, but, 

 as I shall show, cases of reversion are often much more extensive. 

 The progress of reversion is sometimes slow and sometimes sudden, 

 the whole change in the latter case often occurring in a single genera- 

 tion. The effect is much the same whether the degenerating process 

 is sudden or slow; and however widely the improved varieties may 

 have differed from one another, the reversional trend of all is towards 

 the comparatively small globular berry that may be properly regarded 

 as the primitive tomato fruit form. In slow degeneration the fruit 

 begins to ripen unevenly; it diminishes in size and becomes com- 

 paratively soft, and has a rank taste. The walls and dissepiments 

 become thin, the seed compartments are reduced to four, three, and 

 even to two, and the seed pulp is more abundant and more watery. 

 In sudden reversion the primitive berry condition is reached, or ap- 

 proached, at a bound. These remarks concerning degeneration apply 

 especially to the varieties which have arisen from L. esculentum, as 

 delimited, of which cases only I have had personal knowledge. 



With the possible exceptions which were merely suggested in a 

 previous paragraph, the duration unimpaired of any of the highly 



