DURATION OF VARIETIES OF PLANTS. 



ON THE LIMITED DURATION OF VARIETIES OF PLANTS. 



BY JOHN TOWNLEY, MOUNDVILLE, WIS. 



A. J. Downing, Esq. — Dear Sir: I accede with pleasure to the request of your corres- 

 pondent, Mr. Marshall, to state what grounds I have for subscribing to the theory ad- 

 vanced by Andrew Kkight, respecting the limited duration of varieties of plants. 



Before I proceed, however, I wish to set Mr. Marshall right on one or two points; he 

 says that I condemn propagation by extension in comparison with seedlings; if what I 

 have said should convey that meaning to your readers generally, some apology is due from 

 me for the imperfect manner in which I must have expressed myself, for I certainly do not 

 condemn propagation by extension; on the contrary, I consider that when once a valuable 

 variety of apple, &c., is obtained from seed, that multiplying it by divisions of the stem 

 is a perfectly legitimate mode of propagation, and one that should be practiced so long as 

 the individual variety retains its health and vigor; but beyond that period — when a vari- 

 ety exhibits manifest symptoms of declining vigor, and has become diseased and unpro- 

 ductive, through age, then I consider it should no longer be propagated by division, nor 

 should seeds be saved from it with a view to raise new varieties, seeing that it is probable 

 that the health of the seedling plants would be influenced to some extent by the unhealthy 

 and degenerate condition of the parent tree. 



I may further remark that I am not prepared to prove "that trees and plants propa- 

 gated by extension, do produce degenerate fruit from that very cause, and that alone." I 

 am not aware of having said anything in the paper referred to, which will justify the con- 

 clusion that I entertain an}' such notions. In the matter of the potato, I stated what I 

 believe to be the exciting and chief predisposing causes of the blight; I consider the pota- 

 to to be in a condition diiferent from that of any other cultivated plant; that considered in 

 the mass, or as a species, it is hereditarily diseased; believing this, and knowing that it 

 had been observed in the case of the pear, that seedlings raised from old, nearly worn out 

 varieties, proved, as might reasonably have been expected, unhealthy, and liable to disease 

 also; and knowing, moreover, that many varieties of potatoes recently obtained from seed, 

 were subject to dry rot, and as much injured by the blight, as older varieties, I concluded 

 that the best way to get rid of the hereditary taint, was to persevere in raising a succes- 

 sion of seedlings, with improved culture, selecting the strongest and healthiest plants each 

 year, to be the parents of a fresh generation of seedlings in the year following. If seeds 

 were saved from a healthy variety of fruit tree, or other plant, Avhen in the prime of its 

 existence, although the plant it was saved from had been propagated by extension, I know 

 of no reason why the progeny should not be perfectly healthy. Nor is there any reason 

 for believing otherwise, than that a species of plant whose varieties are propagated by ex- 

 tension, may not be continued equally healthy and vigorous forever, providing the succes- 

 sive generations of seedling varieties were always raised from seeds taken from plants 

 when in a healthy and vigorous condition. 



Now for my " hobby." Perhaps it may be well at the outset to state briefly the nature 

 of the hypothesis we are about to consider. It is this. Vegetable life, like animal life, 

 has its fixed periods of duration. A seedling apple tree, for instance, has its periods of 

 youth, maturity, and old age. All cuttings taken from this seedling apple tree and graft- 

 but the extension of an individual plant — one distinct variety, and the plants 

 ated possessing the same constitution, properties and tendencies, and are not 



