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disease extensively prevalent in sweet potatoes. It was very- 

 destructive in its character, rapidly extending throughout a large 

 quantity of them where one had become affected with it, redu- 

 cing the potato to a soft-solid pulp. On examining it with the 

 microscope he had found two species of fungus similar to the 

 fungus in the common potato affected with the rot. Large num- 

 bers of flies of the species Antliomyia radicum 1 issued from 

 the barrels containing the diseased potatoes, but he thought they 

 had no connection with the origin of the disease, but were propa* 

 gated on their surface. 



Mr. Russell said, he felt confident after numerous investiga- 

 tions, that the fungi were not the cause of the rot in potatoes, 

 they were only a consequence. He thought the rot to be either 

 analogous to dry gangrene or else quite inexplicable. 



Mr. Russell presented a package of specimens of Lichens 

 and Musci, collected at Lake Superior by Mr. Desor. He 

 said, that he had examined under the microscope sections 

 of the wood from the terraces of Lake Superior, thought 

 by Mr. Desor to be cedar, and had ascertained that they 

 were not cedar, but some hard wood. 



Mr. Alger offered some remarks on a singular cavity 

 presented by one of the quartz crystals from Waterbury, 

 Vermont. 



He said that he had, on a former occasion, called the attention 

 of the Society to the beautiful crystals from Waterbury, which 

 were permeated in every part by acicular prisms of rutile. He 

 wished now to exhibit a specimen which had recently come into 

 his possession, and which was marked by a peculiarity hitherto 

 unobserved. It presented on one of its transparent faces a 

 rhomboidal cavity, one inch in width, and about half an inch in 

 depth. It might at first sight be mistaken for the impression left 

 by some substance which had become surrounded by the quartz, 

 and had since disappeared by decomposition. But no substance 

 having such form had been found attached to any of the crystals 

 from this place, nor did it seem probable that any crystallized 

 mineral could assume the exact conformation required to fill up 

 the cavity. The angles at which the sides meet each other are 



PROCEEDINGS B. S. N. H. 18 JULY, 1850. 



