NATURAL SCIENCES OF PHILADELPHIA. 129 



description has been published, as R. neglectus, Peck. This form is found in 

 isolated places in New York, Northern Pennsylvania, Ohio, ami Lown, and per- 

 haps elsewhere. As in the case ot the form of R. villosus referred to, there 

 does not seem to be any connection between the localities, as a common cen- 

 tre spreading by roots would imply, while there is the same difficulties in the 

 way of spreading by seeds as in the other. How, then, does this form origi- 

 nate in these widely separated places. 



Horticulture may help us to answer this question. It is well known that 

 fruits, after being grown for some time in one locality, will change their char- 

 acters to such an extent that a person acquainted with one will fail to recog- 

 nize it elsewhere, and all this without the intervention of any seminal power. 

 Thus, the nectarine is believed to be a bud evolution from a peach ; the Penn 

 apple is a similar creation from Baldwin, and the Reading from the common 

 Isabella grape. Though apparently originating in this way from external or 

 local causes, the characters peculiar in this change are retained when, by 

 grafts or cuttings, the plants are removed to other localities. It has also been 

 noted that the pears grown at Rochester, New York, have longer stems than 

 the same varieties grown further south ; but I do not know whether this pecu- 

 liarity, once originated, would follow the grafts or cuttings taken from them. 

 The curled-leaved willow, Salix babylonica annularis, was a branch from the 

 common weeping willow, which character it usually retains, though sometimes 

 a branch, resembling the common weeping, will push out from the tree. Of 

 like character is the well-known instance of purple-flowered laburnums some- 

 times pushing out from the common yellow-flowered one. But perhaps the 

 best known iustances are those of the common potato. It is not at all unfre- 

 quent to find some of quite another character and color in the same hill. 

 Those who contend for seed agency as the sole originator of varieties will 

 rather believe that there was some other variety of potato accidentally planted 

 with the other than that a new variety sprung from the bud alone. But the 

 evidence of origin from the same original potato-set has, in many instances, 

 been too direct to be doubted; but, even here, rather than admit the doctrine 

 of development through buds, I have heard it assumed, by intelligent botanists, 

 that the flowers in such cases must have b-en impregnated with other pollen, 

 and, in some way, the descending sap brought about a sort of hybridism or 

 bud change in these tubers. I have also heard excellent and leading botan- 

 ists (two of them authors of some of our leading works) suggest that many 

 of the varieties of Rubus in existence must be " hybrids." Of course, this is all 

 assumption, founded on extensive observation, no doubt ; but yet on probably 

 no better foundation than my own idea with which I set out in this paper 

 that often, at least in the cases I have referred to, hybridization is highly im- 

 probable. 



I have here, however, and exhibit with this paper, evidence of bud varia- 

 tion, in which there is no possibility of hybridism. A root of the common 

 sweet potato, Convoleulus batatas, in which some of the tubers are of the red 

 Bermuda, and the others of the white Brazilian variety. 



The sweet potato never flowers in this part of the country, so that seminal 

 power could have had no influence whatever on the phenomenon. Even in 

 the south, and I believe elsewhere, where this plant is cultivated for its roots, 

 it rarely flowers, and I think there is little doubt but that the whole ten or 

 twelve varieties under culture have originated without seed, and in the way 

 we see them here. 



The points I wish to make in this paper are : 



1st. That identical varieties sometimes appear in localities unfavorable to 

 the idea of a common centre of origin. 



2d. Varieties have originated in which probably no hybridism or any seminal 

 agency operated. 



3d. Varieties have certainly originated in the sweet potato by evolution, 



1870.J 



