228 THE AMERICAN NATURALIST [Vol. XLII 



far as can be ascertained from the universal experience 

 of those who are conversant with them, as well as from 

 everything that can be gathered from the records of 

 remote antiquity, to remain distinct from each other, 

 marked by their appropriate characters and qualities, 

 and renewing themselves periodically by sexual genera- 

 tion. Such being the case with all the plants of which 

 we have any knowledge, we conclude it to be so with the 

 rest, as well as with animals. The white blackbird of 

 Aristotle still inhabits the Cyllenian groves and copses 

 of Arcadia, undisturbed by the revolutions of two thou- 

 sand years; and we doubt not that the banks of the 

 Alpheus have been fringed with the same violets and 

 primroses, through uncounted ages, as those with which 

 they are now, every spring, adorned. 



Various plants indeed, and especially domestic ones, 

 like domestic animals, are found liable to some varia- 

 tions of color, luxuriance, and sensible qualities, which 

 have led curious inquirers to doubt whether any species 

 are certainly permanent. This doubt could arise only 

 from a slight view of the subject. ^AHiatever casual 

 aberrations there may be in the seminal offspring of 

 cultivated plants, a little observation will prove how 

 transient such varieties are, and how uniformly their 

 descendants, if they be capable of producing any, resume 

 the natural characters of the species to which they belong. 



From A. P. DeCandolle and K. Sprengel, Elements of 

 the Philosophy of Plants, Edinburgh, 1821. 

 By species we understand a number of plants, which 

 agree with one another in invariable marks. 



In this matter everything depends upon the idea of 

 invariableness. When an organ, or a property of it, 

 is changed neither by difference of soil, of climate, or of 

 treatment, nor by continued breeding, this organ or prop- 

 erty is said to be invariable. When, for instance, we 

 have remarked during centuries, that the centifolia has 

 always unarmed leafstalks, we say correctly, that this 

 property of the centifolia is invariable. 



