30 BULLETIN 179, U. S. DEPARTMENT OF AGRICULTURE. 
The tree attains a maximum height of about 40 feet and occurs 
singly or in groves, but never suckers or forms thickets. The bark 
of the trunk exfoliates in platelike scales when young, later becoming 
furrowed, while the larger branches retain the bark character of the 
young trunk; the bark of the twigs at flowering is usually grayish, 
that of the young growth in summer dull chestnut. . 
Prunus mexicana occurs (fig. 1) In open woods in rich alluvial bot- 
tom lands, on the upland prairie soils, and even in sandy loam, and 
ranges from southwestern Kentucky and western Tennessee south- 
westward through northwestern Louisiana to the vicinity of Lerios, 
Coahuila, Mexico, the type locality, and central Nuevo Leon, where 
scattered trees occur on the northern slope of the Sierra Madre at 
about 3,000 feet elevation. Its range extends westward through the 
extreme southern part of Missouri to central Oklahoma and central 
Texas. 
Prunus mexicana varies somewhat, but not more so than may be 
expected in a species of its range. Specimens from Feliciana Parish, 
La., have the calyx tube entirely glabrous, except for a few longish 
hairs toward the base, with pedicels 17 to 18 mm. long. The calyx 
tube in Arkansas-specimens, P. polyandra and P. arkansana Sarg., is 
less pubescent than is usual in Texas material, but is somewhat 
variable in this respect even in the same locality. <A form, P. tenui- 
folia Sarg., in the vicinity of Larissa, Cherokee Co., Tex., shows the 
greatest departure from the usual character of the species of any 
observed, since it has a finely pubescent calyx with a few longish 
hairs toward the base and on the pedicels, while the immature fruit 
indicates an oblong stone. P. reticulata Sarg., was described from 
Grayson County, Tex. The original material of the species published 
by Sargent has been studied, and the characters on which they are 
based were very carefully considered. They are all of the type known 
as the big-tree plum, and horticulturally these differences are of less 
importance than variations in what is still recognized as a single 
species in P. americana. The rank to be assigned the forms under 
discussion depends upon one’s conception of what constitutes a 
species. | 
Although long confused with Prunus americana and in the her- 
barium sometimes difficult to distinguish from P. americana lanata, 
the species is nevertheless a very distinct one. It never forms thick- 
ets, as does P. americana and its subspecies, but occurs always as a 
tree with a well-defined trunk, which in the older trees differs in its 
furrowed bark. The young leaves as they appear are mostly some- 
what obtuse at the apex instead of acuminate; the older leaves are 
usually broader in proportion to their length, and the serration of 
the margin is slightly less pronounced. The flowers also have petals 
somewhat broader in proportion to their length than in P. americana, 
while the stone is obovoid or round and more turgid. | 
