36 ESSAYS. 
weed,” as Dr. Darlington, agriculturally speaking, terms this 
showy plant, is occasionally seen along the roadside in the 
northern States; but here, for the distance of more than a 
hundred miles, it has taken complete possession even of many 
cultivated fields, especially where. the limestone approaches 
the surface, presenting a broad expanse of brilliant blue. It 
is surprising that the farmers should allow a biennial like this 
so completely to overrun the land. Another plant much more 
extensively introduced here than in the north (where it 
scarcely deserves the name of a naturalized species) is Bu- 
pleurum rotundifolium, which in the course of the day we met 
with abundantly. The Marrubium vulgare is everywhere nat- 
uralized ; and Luphorbia Lathyris must also be added to the 
list of naturalized plants. The little Verbena angustifolia is 
also a common weed. We collected but a single indigenous 
plant of any interest, and one which we by no means expected 
to find, namely, Carex stenolepis of Torrey,’ which here, as 
in western States, to which we supposed it confined, takes the 
place of the northern C. retrorsa. We searched for its con- 
stant companion, C. Shortii, and the next day we found the 
two growing together. During the day’s ride we observed 
that the bearded wheat was almost exclusively cultivated, and 
were informed that it had been found less subject to the ray- 
ages of the “ Fly” than the ordinary varieties; which may be 
owing to recent introduction of the seed of the bearded variety 
from districts unmolested by this insect. 
The following day we traveled only sixteen miles on our 
route, but from Mount Sidney made an interesting excursion 
on foot to Weyer’s Cave, one of the largest, and certainly the 
most remarkable grotto in the United States. It has been so 
often described as to render any account on our part super- 
1 It is the C. Frankii of Kunth (1837), and of Kunze’s Supplement to 
Schkuhr’s “Caricography,” where it is well figured. It was also distrib- 
uted among Dr. Frank’s plants under the name of C. atherodes, and with 
the locality of Baltimore in Pennsylvania! I had always supposed it to 
be derived from some part of the western States ; but since it abounds 
in the Valley of Virginia, it may have been collected near Baltimore, 
Maryland. 
