MIDDLESEX FLORA. 81 



Mentanthes, Tourn. 



M. trifoliata, L, Buckbean. 

 Not uucommon. May. 



LiMNAXTHEMUM, Gmel. 



L. lacunosum, Griseb. Floating Heart. 

 Throughout the county, but nowhere very common. July-Aug. 



APOCYNACE^. DOGBANE FAMILY. 



Apocvnum, Tourn. 



A. androsaemifolium, L. Dogbane. 



Common. June-July. 

 A. cannabinum, L. Indian Hemp. 



Everett, Woburn, Townsend, et al. ; not common. June-July. 



ASCLEPIADACE>^. MILKWEED FAMILY. 



ASCLEPIAS, L. 



(^ A. Cornuti, Decue. Milkweed. 



Very common. July-Aug. 

 A. phytolaccoides, Pursh. Poke Milkweed. 



Generally distributed, but not common. June-July. 

 A. purpurascens, L. Purple Milkweed. 



Not very common. July-Aug. 

 1, A. quadrifolia, L. Four-leaved Milkweed. 



Not very common. June. 

 A. incarnata, L., var. pulchra, Gray. 



Common. July-Aug. The type, though often reported, does not 



appear to be within the county limits. 

 A. obtusifolia, Michx. 



Not common. A form with the leaves in whorls of three was found 



at Concoi-d by W. H. Manning. July-Aug. 

 A. obtusifolia X phytolaccoides, (yicZe Asa Gray) . 



Several plants were found along the banks of the old Middlesex 



Canal in Wilmington, July, 1885. 

 A. tuberosa, L. Butterfly-weed. 



This plant, frequently mentioned by the older botanists, has become 



rare, at least in the vicinity of Boston. July-Aug. 

 A. verticillata, L. Whorled Milkweed. 



Maiden, Woburn, Frainiugham, Natick, et al. Not common. July- 

 Sept. 



