298 ROYAL SOCIETY OF CANADA 
small to medium tracts which are more or less distant and constantly 
diminishing in size outwardly, sometimes forming diagonal or even 
tangential series, the contained vessels often lying in radial series of 
2-4. Medullary rays poorly defined but rather numerous and several 
cells wide. 
Radial.—Medullary ray cells all of one kind, straight, rather thin-walled with no 
recognizable markings. Vessels short and broad, the radia] walls 
with multiseriate and chiefly hexagonal, bordered pits. 
Tangential Rays numerous, low and broad, upwards of 4 cells wide and never 
uniseriate. Vessels as in the radial section. 
250 L © 
re of 1905. ULMUS PROTOAMERICANA, n. sp. 
Df 
Plate VII. 
9 
The specimens designated as a represent another species of 
Ulmus in a very perfect state of preservation which permits of drawing 
a diagnosis with completeness. Whatever doubts may attach to the 
preceding species with respect to its relation to existing forms, there 
seems to be little or no room for denying the relation of the present 
material to the existing American elm, of which it is undoubtedly the 
ancestral form. The most prominent respect in which it differs appears. 
to be in the rather broad zone of vessels in the spring wood, and the 
somewhat different form presented by the distribution of the wood 
parenchyma in the summer wood. Both of these features are of a 
variable character in the white elm and quite conformable to what is. 
found in the fossil. 
That both U. americana and U. racemosa should be represented in 
the same formation by equivalent forms, is in no way surprising when 
we recall their constant association in the Pleistocene and also in 
existing floras. There is therefore no reason why the prototypes of 
these familiar species should not be similarly associated in the early 
Tertiary. The diagnosis of this species is as follows :— 
ULMUS PROTOAMERICANA, n. SP. 
Transverse—Growth rings variable, often very narrow, with no obvious dis- 
tinction between spring and summer wood except through the location 
of the large vessels. Wood cells at first rather large and rather 
thin-walled, soon reduced and passing somewhat gradually into small, 
thick-walled cells at the outer limits of the growth ring, very variable: 
and unequal throughout, rarely disposed in radial rows, the structure 
dense. Vessels at first large and prominent, often with round or oval. 
transversely or more generally radially 2-3 seriate; forming a zone 
14 to % the thickness of the growth ring and abruptly followed by 
smaller vessels with wood parenchyma which form tracts of variable 
extent, radially or transversely extended, or more or less coalescent so- 
as to form diagonal tracts or tangential zones of indefinite extent ;. 
