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pany oF my friend C. C. Frost on the rocky sterile slopes 

 of a hill of granite called Bald Mountain, near Dummerston, 

 Vermont^ and with small success, we struck on our descent 

 uiDon a brook, through whose bed we wended our way, hoping 

 that the water might prove more auspicious than the dry, sun- 

 burnt rocks. Nor were we disappointed as the result proved. 

 Our delight was as mutual as it was unexpected, when t drew 

 from the stream an aquatic lichenose plant diffusing a grateful 

 aroma not Unlike that of the bark of the black birch, and co- 

 vered with apothecia, every part in perfect condition, which I 

 plucked from the bottom of the brook. 



Subsequently this same plant occurred to me m abundance 

 growing upon the rocks and stones, over which in the Spring 

 months a flood of water is poured from Wantasquit mountain, 

 near Brattleboro', Vt., at a place called the Cascade. This 

 little brook becomes entirely dried for a part of the year in the 

 middle of summer ; though suffused by temporary rains and 

 showers at that period, and visited by more or less water for 

 the remainder of the time. 



On the thirteenth of September, 1852, I again detected this 

 plant in a small cold stream, which issued from the foot of 

 Mount Crawford, one of the White Mountains in New Hamp- 

 shire. Here it was not very plentiful, but was in fine condi- 

 tion, and was pronounced new to the flora of that region. 



The thallus of the Hydrothyria is rather thin, the interior 

 composed of mucilage in which there are many minute granules 

 having no regular arrangement nor any approximation to a 

 moniliform character ; instead of which the hyaline filaments 

 are quite numerous and far more abundant than in collema or 

 in leptogium. The epidermis is composed of tissue intricately 

 netted or cellular, but of no regular outlines and whose 

 filaments anastomose into each other. 



In the structure of the veins we see a nearer approach to the 

 true lichens, inasmuch as the central parts of each vein compose 

 a sort of medullary layer of similar anastomizing fibres envel- 

 oped by strong, thickened and somewhat quadrangular cells. 



