36 ESSA VS. 



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 Marubium vulgare is everywhere nat- 

 uralized ; and Euphorbia Laihyris 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 stenolepsis of Torrey, 1 which here, as 

 in western States, to which we supposed it confined, takes the 

 place of the northern C. retrorm. 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 rav- 

 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 " Cartography," 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. 



