xlii 



Mr. C. V. Riley admitted that such was the general belief 

 among botanists and mycologists, but cited some instances of rot 

 in fruits and vegetables which led him to believe that fungi were 

 sometimes the effect instead of the cause of the rot. 



Dr. J. B. Johnson questioned whether they might not be the 

 effect rather than the cause, just as certain fungi are known to 

 follow the injuries caused by the itch mite- {Acarus scabiet)^ on 

 the human subject. 



Mr. H. T. Mar^e de Beauregard, of St. Louis ; A. Hager» 

 State Geologist, and H. N. Spencer, M.D., of St. Louis, were 

 elected associate members. 



March 6, 187 1. 



The President in the chair. 



Eight members present. 



Exchanges received were laid upon the table. 



Dr. Engelmann exhibited three specimens of the Abutilon 

 Avicennce (Indian Mallow), the common weed which is coming: 

 into use for paper-making, as stated at a former meeting. They 

 differed but slightly — one being from St. Louis County, one from 

 the south of France, and one from Italy. 



Mr. C. V. Riley asked if Dr. Engelmann had any explanation 

 of the fact, that so many of our commonest plants and weeds 

 were introduced from abroad, and had become naturalized here, 

 while so few of our plants had become naturalized in Europe. 

 He had shown in his second I'eport that no less than 233 distinct 

 species, excluding from consideration all cryptograms, all doubt- 

 ful cases, and all cases where the same plant is supposed to be 

 indigenous on both sides of the Atlantic, had been introduced 

 into this country from Europe, and that no less than forty-three 

 were most pernicious weeds. 



In insects, the same facts obtained ; for while dozens of our 

 more injurious species are of European origin, but two or three 

 American species had ever become greatly multiplied there. 



Dr. Engelmann thought that no theory was necessary, as such 

 a state of things was to be explained by the fact that some plants 

 are more vigorous than others. He was also disinclined to be- 

 lieve that there was such a contrast. 



