14 Rhodora [JANUARY 
found that “the cottonwood most common in Washington, known 
as the South Carolina poplar, could not be infected by the uredo form 
[of Melampsora sp.] from the common Western cottonwood, although 
these two poplars are classed by some as being the same species. More- 
over, the rust does not occur in nature on the South Carolina poplar, 
but is very abundant on the Western cottonwood, and even occurs in 
Washington on the few individual trees of that type growing in the 
city.” The cottonwood most common in Washington, “known as 
the South Carolina poplar,” is P. deltoides. The few trees of the other, 
called by Mr. Carleton “the Western cottonwood” are the same in- 
dividuals upon which Mr. Tidestrom based his report of P. virginiana 
“in cultivation.” 
Doubtless our poplars hybridize extensively. This fact renders 
their study difficult, especially if herbarium material only is dealt 
with. Botanists who are favorably situated to do so, would, I am 
sure, confer a great favor upon Mr. Tidestrom by communicating to 
him poplar specimens and notes concerning them. 
BETHESDA, MARYLAND. 
Nores on BorrycuiuM FROM TENNESSEE.— The occasion of these 
notes on the Genus Botrychium was the finding of a peculiar terato- 
logical specimen of obliquum Muhl. Upon the sterile frond there are 
several pinnae which bear groups of well developed sporangia. In 
every case in which there are several sporangia together a definite 
rhachis connects them. This rhachis is composed of a portion of the 
frond which is slit out of the leafy tissue. A line of tissue of lighter 
green color than the rest, runs out to this rhachis. The sporangia are 
perhaps a little smaller than the average of the sporangia that are 
borne on the fertile frond, and the spores are between four and five 
percent smaller than the normal. The viability of the spores was not 
tested, but in appearance they were in no appreciable way different 
from the normal. There was only the one plant of the species found 
in the locality, which was not far from Knoxville. 
This species does not seem to be very common in the parts of East 
Tennessee which have been examined by the writer, and there are 
only three specimens of the plant from the entire state in the university 
herbarium. Two of these are from Middle Tennessee and the other 
from West Tennessee. The writer has collected it from only one other 
