843 



this way convert a low meadow or pasture into a poplar grove. That 

 such is the origin of many of our gray and white poplars in this island 

 I cannot doubt ; but as the trees would have the same tendency to 

 increase by suckers from the widely-creeping roots, whether aboriginal 

 or not, this mode of propagation affords no argument one way or the 

 other, excepting so far as it readily accounts for the spreading of the 

 species in spots where it has been certainly introduced. With regard 

 to P. nigra, I confess to doubts somewhat more decided ; no station 

 in which I have ever seen the black poplar appeared to my eyes 

 above suspicion. 



The question now comes to be considered, are P. alba and P. ca- 

 nescens distinct, or are they varieties of one and the same species ? 

 My own opinion inclines strongly to the belief of their being identical, 

 and that the former is but a state of the latter originating from culti- 

 vation or quality of soil inducing a greater development in the leaves; 

 that they are in fact analogous to Tilia europaca and T. parvifolia, 

 which are pretty generally admitted to differ only in the size of their 

 leaves and a few minor points of no specific importance. Hence both 

 these poplars may grow equally wild, but the Abele will oftener be 

 seen in suspicious stations than the gray aspen, and this accords with 

 observation. What lends countenance to the opinion just expressed 

 is, that I find people not always agreed as to what is P. alba or what 

 P. canescens, and in fact I am sometimes at a loss how to name cer- 

 tain individuals of these species, so nearly intermediate betwixt both 

 do they present themselves occasionally. By P. alba or Abele I un- 

 derstand a great tree very common in plantations about houses, or in 

 water-meadows, having large triangular or trowel-shaped leaves, all 

 deeply and conspicuously angular, toothed and lobed, the under sur- 

 face snow-white ; by P. canescens a tree sometimes of equal height 

 and bulk with the Abele, but with usually smaller leaves, for the most 

 part of a roundish rather than triangular figure, much less deeply an- 

 gular, and mostly obscurely lobed, excepting those on the youngest 

 trees or the suckers, which are hardly distinguishable from the leaves 

 of the Abele in size or shape, and pretty clearly prove how much an 

 excess of moisture or nourishment has to do with determining these 

 differences in the foliage. The leaves, indeed, of P. canescens are 

 extremely variable in form on the same tree, and in general approach 

 those of the common aspen {P. tremula) in outline, that is, they are 

 often rounded and but slightly pointed at the apex, and instead of being 

 angular and lobed are merely sinuate, or sinuate-dentate. Under- 

 neath, the leaves of P. canescens are as white sometimes as in P. alba, 



