Geology discloses to us the fact, that at certain periods of time species 
began to exist, and that it was only after the lapse of untold ages that 
they cease to be. It discovers no particular season for their rise or de¬ 
cline, or why certain species should hare appeared at one period of time 
rather than at another. It shows that a single species, springing from 
some primitive centre, distributed itself over the face of the globe, or 
over certain definite areas, by the slow process of dissemination, and 
flourished during immensely extended periods of time, without any ap¬ 
parent diminution of vitality, or any change in its generic ties. The re¬ 
mains of the primitive flora show that vast vegetable migrations have 
taken place upon the globe at different periods of time ; and that the dif¬ 
ferent species of plants, springing from various and widely separated 
centres, have gradually covered the earth with their vegetation and prop¬ 
agated themselves by seed, bud or scion, for many thousands of years. 
It is utterly impossible, then ; nay it is assuredly so ; that human obser¬ 
vation should be sufficiently extended to furnish the requisite data of 
testing the wearing-out theory. 
We are speaking now of the theory in its application to the potato as 
a species; for it is contended by its advocates, that the plant, ‘ considered 
as a species , has progressively deteriorated ;* and the cause of this deter¬ 
ioration is attributed to the manner in which it has been propagated. 
But our answer to this is, that nature understands her own economy ; 
propagates in her own quiet way ; and always with a view to the consti¬ 
tutional hardiness of the species. If she directs her efforts at reproduc¬ 
tion through the seed-eyes of the tuber, instead of elaborating seeds in 
the pericarps of the potato, it is because she adapts herself to the wants 
of tlie plant and to the circumstances under whi®h it is engendered. She 
always avails herself of the requisite material at hand—of the immediate 
resources of the plant to be propagated, and invariably selects the method 
best adapted to its wants. This is true not only in regard to individual 
species, but to the plant in all its collateral relationships, generic branches, 
and hereditary ties. In every instance, nature adapts her means to the 
specific end. If a rose-bush be transferred from a rich to a dry and arid 
soil, it ceases to extend itself by runners, and naturally runs to seed ; 
whereas, if the same bush was transferred from a dry and arid to a rich 
and fertile soil, it would just as naturally extend itself by runners, in¬ 
stead of elaborating seed. And for the simple reason, that there would 
