90 
on the former, I suppose they were seedlings. On these small 
trees the tomentose leaves remain until they naturally drop off 
in the autumn, and I have so far seen but a single one of the 
two types on the same individual tree. The age when the nor- 
mal leaves first appear I have been unable to determine, and it 
may vary in different localities; the tomentose forms were, how- 
ever, seen on plants eight to ten feet high. The text-books 
make no allusion to this remarkable variation in leaf-form, nor 
have I been able to find it recorded in any literature at my com- 
mand; frequent mention is made of the woolly surfaces of ordi- 
nary young leaves, a feature which exists even on those of large 
trees. The system of primary nervation is much the same in 
both types, though in the leaves of the saplings here alluded to, 
the mid-veiu is straighter, and the disposition of the veinlets dif- 
fer also in details. 
Populus grandidentata was named by the elder Michaux 
(Flor. Bor. Amer., ii., p. 243.) He notes the villose younger leaves, 
but makes noreference to the serrulate ones of saplings. P. hetero- 
phylla is a Linnean species, (Spec. Plant., 1st Ed., p., 1034; 
3d Ed., p. 1464), but the diagnosis given is simply ‘Populus 
foliis cordatus primoribus villosus.” Now, a question arises as 
to which species Linnzeus actually had. The above short de- 
scription might apply equally well to the leaves of both, now that we 
have shown the character of sapling leaves of P. grandidentata. 
It would appear that Linnzeus had not seen the fruit. The leaves 
of the Swamp Poplar, (P. heterophylla), so far as the living trees 
and herbarium specimens which Ihave seenrepresent it, vary 
very little in shape; they are quite uniformly broadly ovate, 
obtuse, and generally though not invariably cordate, so that the 
Linnean name does not well apply to them. In the Sylva 
Americana the tree is called Populus argentea, which is a better 
name for it, while /eterophyl/a would apply very well to the 
Large Aspen. Is it possible that Linnzeus was aware of the var- 
iation described at the present time? The two species are very 
distinct, the racemose fertile inflorescence of the Swamp Poplar 
being characteristic, and not met with, I believe, in any other 
American species. In fruit the pedicels become half an inch or 
more in length, a character noted in Wood’s Class Book. 
