170 Rhodora [OCTOBER 
stations as possible and to obtain field information on the extent of 
naturalization which the species has undergone. In the course of 
this investigation many new stations have been discovered and much 
detailed data gathered on the local distribution of the species. 
Through the attention directed to it, each year adds its quota of 
information to our knowledge of the occurrence of the plant, so that 
there is now sufficient data to show that the species has become 
naturalized thoroughly in many places in the Philadelphia area— 
much more so, in fact, than many a shrub or tree that, not infrequently 
upon very scanty evidence, has long had a place in our flora, 
Prunus Padus is a small tree occurring natively in the northern 
portions of the Old World. Although it is sometimes credited with 
being common in cultivation in America, there is little evidence that 
it is in any present demand. Very few nurserymen have it for sale 
or even catalogue it. It appears to have been rather popular in 
America years ago, but now it has rather lapsed into the category of 
“a plant of old gardens.” 
There are few more attractive woody species to be seen about 
Philadelphia. By mid-April the leaves are already unfolding and 
the plant is bright and green, while thickets and woods are still brown 
or brightened only by the flowers of the Spice Bush. With the first 
days of May (or the end of April in early seasons) the plant is covered 
with long racemes of white blossoms. The flowering season, as in so 
many trees, is quite short, scarcely over a week or ten days, and within 
a few weeks the fruit develops sufficiently to show the characteristic 
roughened stone. Late June to early July brings the brief season of 
ripe fruit. 
In some characters this plant closely simulates the native Choke 
Cherry, Prunus virginiana, and in others, the Wild Black Cherry, 
P. serotina. The former does not occur in the immediate vicinity of 
Philadelphia and has not been found in the area where P. Padus 
is naturalized, but P. serotina is a common “weed” tree about Phila- 
delphia and a frequent associate of P. Padus. The habit of P. 
Padus is distinctly arborescent and the bark quite dark. In these 
characters it resembles P. serotina. In winter, or in early spring 
when the leaves are just unfolding, there is frequently considerable 
difficulty found in distinguishing it from the Wild Black Cherry. 
The Choke Cherry, however, is characteristically a shrub, rarely 
attaining tree-like proportions, with bark more inclined to be grayish. 
