94 MIDDLESEX FLORA. 



COMPTONIA, Soland. 

 C. asplenifolia. Ait. Sweet Fbkn. 

 Common. Apr.-May. 



BETULACEy^, BIRCH FAMILY. 



Bettjla, Tourn. 



B. lenta, L. Cheeet Biech. Sweet or Black Biech. 

 Widely distributed. Frequent. Apr.-May. 



B. lutea, Michx, f. Yellow Birch. 

 Not as common as the preceding species. Apr.-May. 



B. alba, L. var. populifolia, Spach. American White. Birch. 

 Gray Biech. 

 Common. May. 



B. papyracea. Ait. White Biech. Paper or Canoe Biech. 

 Rare eastward, but common in other sections of the county. May- 

 June. 



B. papyracea. Ait., var. minor, Tuckerm. Dwarf Canoe Biech. 

 A clump of trees 6 or 7 feet high, growing in a swamp in Lexing- 

 ton, 1875 (Minot Pratt). 



B. nigra, L. Kitee Birch. Red Birch. 

 Native only in the Merrimac River Valley. 



Alnus, Tourn. 



A. incana, Willd. Black Aldee. Speckled or Hoaet Aldbe. 



Common. Mch.-Apr. 

 A. serrulata, Willd. Smooth Aldee. , 



Less common than the preceding species. Mch.-Apr. 



SALICACEyE. WILLOW FAMILY. 



Salix, Tourn. 



S. tristis. Ait. Dwarf Gray Willow. 



Not uncommon. Apr.-May. 

 S. humilis. Marsh. Praieie Willow. 



Rather common. " The intermediate character of this species, as 



between S. tristis and S. discolor was long ago pointed out by Mr. 



Carey. The confusing forms appear to be hybrids." — M. S. Bebb, 

 S. discdlor, Muhl. Glaucous Willow. 



Common. Forms with anthers transformed to ovaries, occasional. 



Apr.-May. 



