NOTES ON POPULUS, PLINIUS 31 
compresst. Stylus brevis. Stigmata 2, valde dilatata, recurvata, 
trregulariter quadriloba.”’ 
There is a great deal of variation both as to form and size of the 
‘leaves in this species. In normal leaves the petiole is nearly as 
long as the lamina, and sometimes longer. In specimens which 
I collected near Stockholm in August, 1897, the laminae are 7 cm. 
more or less in length and fully as wide, while the length of the 
petioles is fully 5 cm. The root-shoot leaves are cordate, acute, 
while normal leaves are rounded, the former are more or less 
pubescent, while the latter are glabrous. The indentation of the 
normal leaves is more or less irregularly crenate-dentate. 
Hartman (Skand. Fl. 187, 1870) mentions two forms of P. 
tremula,—var. serrulata Frist. with small, serrulate leaves and 
var. 2. (P. villosa Lang) with leaves pubescent on both faces. 
Since I have not seen these forms I am unable to discuss them. 
Poplars seem to have had a charm for the early settlers of Mary- 
land; for in every old settlement, as Bladensburg, Annapolis, 
and others which I have visited, they thrive and add much to 
the picturesqueness of these places. P. canescens is the common 
species: this tree was evidently brought over and planted by the 
early colonists. As to its claim to specific rank, there are good 
reasons both for and against it. It is evidently intermediate 
between P. alba and P. tremula. As to leaf form it occupies a mean 
position. In examining the leaves of three species it appears that 
the relative lengths of the petiole and the leaf blade of P. alba 
bear-the relation of 5-10; in P. tremula this relation is normally 
5-5 or 5-6. In P. canescens, on the other hand, the relation appears 
to be a mean between P. alba and P. tremula or 5-8. Besides, 
the full-grown leaves of P. alba are permanently white tomentose 
beneath and glabrous in P. tremula, while in P. canescens I have 
observed forms unlike in no appreciable way except as to pu- 
bescence on the lower face of the leaf. Normally the pubescence 
of the lower face of the leaf of P. canescens is a scant gray tomentum. 
This character, however, appears to be so variable as to approach 
P. alba in some cases and P. tremula in others. The same might 
be said about the form of the leaves. 
The wood of P. tremula is used in the manufacture of the celebrated 
Swedish matches and also in the wood pulp industry. The leaves 
have served as food for domestic animals in Europe from time 
immemorial. 
