10 



verna, Medford ; Smilax glauca, Weston ; the very rare 

 Habenaria ciliaris, Lexington; Pycnanthemum lini- 

 folium, Reading ; Asclepias verticillata, in several local- 

 ities. 



Perhaps the most peculiar flora occupies the tract lying 

 between Horn Pond Mountain and Winchester, including 

 Winter Pond and a small sheet of water nearly dry in 

 midsummer, to which the name Round Pond has been 

 given by botanists. About the borders of both these 

 ponds grows Coreopsis rosea in abundance ; and on the 

 shores of the former Ludwigia polycarpa, Eleocharis 

 Engelmanni, var. detonsa,ScIeriareticularis, and Cus- 

 cuta arvensis. It is difficult to frame a satisfactory 

 theory for the presence of this little colony. 



Great care has been taken to mark clearly the dis- 

 tinction between species believed to be indigenous within 

 the county limits, and those introduced from without the 

 county, whether from the old world, remote sections of 

 America, or even other parts of Massachusetts. To 

 exclude naturalized species would be to exclude some of 

 our most common plants, and a total of fully one-sixth of 

 our Phanerogams. The difficulty lies in drawing the line 

 between the lately or locally naturalized and the purely 

 adventive. Many introduced plants, now occupying very 

 limited areas, will surely abide with us, if undisturbed by 

 man. They run no greater risk of extermination than 

 many of our attractive native plants. 



There seems to be abundant reason for cataloguing 

 adventive plants, provided their status be appropriately 

 indicated. They are candidates for naturalization. 

 Indeed, when a plant is called indigenous, the term 

 implies simply that, as far back as any record exists, it 

 was a part of the flora. New plants have always been 

 creeping in ; water-courses, winds and birds of passage are 



