BULLETIN 
TORREY BOTANICAL CLUB. 
Vol. XIIL.J New York, June, 1886. {No. 6. 
Leaf-forms of Populus grandidentata. 
By N. L. BRITTON. 
Plate LV1r. 
The difference in the form and outline of leaves borne by 
individual plants of different ages, though belonging to a single 
species, has often been the subject of remark. It is specially 
noticeable in trees, and all are familiar with the variation exhib- 
ited in this respect by Oaks, where it generally appears in larger, 
evidently more vigorous leaves, having less serration or lobing 
on the younger plants than on older ones. To this general habit 
the Poplars are no exception, but exhibit it, in certain cases, to a 
remarkable degree. 
For several years I have repeatedly noticed saplitig Poplars, in 
many places in the woods, bearing very large, ovate-cordate, serru- 
late, commonly somewhat acuminate leaves, their upper surfaces 
glabrous, the lower densely covered with a fine tomentum, which 
under the microscope is seen to consist of slender, simple hairs, 
extending over the very prominent veins, and commonly present 
on the petioles and young shoots. Until quite recently I had 
not been able to ascertain to which species these leaves belong. 
Their outline and serration somewhat resemble those of adult 
Cottonwoods (P. monilifera), specimens collected on the Pali- 
sades in October, 1883, being very much like these in outline ; 
the tomentose lower surfaces suggested P. heterophylla, but no 
large trees could be found. In Angust of last year I obtained 
what would appear to be actual proof that they are borne by 
young trees of P. grandidentata. | first observed the relation of 
the two at a place on the banks of the Morris Canal, near Water- 
loo, New Jersey, while in company with Professor Porter, but 
later noticed it in several other localities. The adult trees of the 
Large Aspen were accompanied by numerous small ones bearing 
the tomentose, serrulate leaves in question. I could not defi- 
nitely ascertain whether these saplings were root-suckers or seed- 
lings, but as I have since been unable to find the peculiar leaves 
