xliv 

 Afril Z-> 187 1. 



The President in the chair. 



Fifteen members present. 



Mr, C. C. Whittelsey mentioned the deposit, by a storm 

 (which occurred on the 15th of March) in various parts of Ohio, 

 of large quantities of a yellow substance which was generally 

 supposed to be sulphur. He suggested that it was the pollen of 

 some tree. 



Dr. Engelmann remarked that it was the pollen of some species 

 of Pine, most probably of the long-leaved Pine, as that was the 

 only species he could think of which was in bloom at the time. 

 This Pine occurs abundantly in Alabama, Mississippi, and 

 also on Red River, and the pollen is often transported at this 

 season by storms coming from those regions. He illustrated on 

 the blackboard the singular form of this pollen, which could 

 always be distinguished from the pollen of ordinary deciduous 

 trees by being trilobed, instead of, more or less, spheroid. 

 The lateral lobes seem to constitute air cells, which assist in 

 floating the pollen through the atmosphere. It also contained 

 oily particles, and burned when ignited, so that the popular idea 

 of its being sulphur was a very natural one. 



Mr. Edwin Harrison observed, that while in the Rocky Moun- 

 tains last summer he had noticed, about the 8th of July, portions 

 of a lake covered with what he at first took to be sawdust, but on 

 closer inspection it proved to be pollen. 



Dr. Spencer had seen pollen fall in New Orleans. 



Dr. Wislizenus cjave an account of the researches of Prof. Ehr- 

 enberg, of Berlin, who made a special study of the deposits 

 of storms, and hoped that members would send the Professor 

 samples of pollen and other materials known to be so deposited. 



Mr. C. V. Riley called attention to the subject of Mimicry and 

 protective resemblances .in animals, and especially in insects. He 

 instanced more particularly the mimicry by an otherwise defence- 

 less butterfly, of one whose great numbers and wide distribution 

 indicate that it enjoys peculiar advantages. He illustrated the 

 only such case known in North America, namely, the imitation 

 of Danais archippus by JLimenitis disippus, exhibiting speci- 

 mens of the insects, and showing that the protection afforded to 

 the disippus by this mimicry enabled it to multiply and become 



