Pe7insylvania for Sessions iSgg-igoo. xxv 



Professor Marsh. Microscopic sections, showing the struc- 

 ture of the organism, were exhibited and described. 



December /j. The President in the chair. Mr. T. C. 

 Palmer read a paper on "The Girdle Structure of Diatoms." 

 Selecting Surirella, Biddulphia and other genera, he showed 

 that the girdle in these was not continuous and inextensible, 

 but had toward one side a fissure, which gave to it consider- 

 able power of extension. Thus it was unnecessary to suppose 

 that a steady decrease in size of the valves took place 

 during division. Mr. Palmer then traced the development 

 of new valves and the origin of the girdle in relation to the 

 valves. 



Dr. S. C. Schmucker submitted " An Annual Report on 

 the Work of the Phytophenological Committee." The 

 results confirmed the view that during the past season vegeta- 

 tion was more advanced than usual. He also dwelt on the 

 dose agreement between the dates for flowering, fruiting and 

 autumnal leaf coloring, as recorded by different obsen.-ers. 

 Miss Mackenzie, Dr. Miller and Dr. Macfarlane made addi- 

 tional observations. 



Miss K. Nicholson then presented " A Review of Experi- 

 ments and Observations on Graft-unions," being a summary 

 of Daniels' recent work on the subject. 



A large exhibit of orchids was made from the University 

 garden. 



Dr. Schmucker exhibited a block of beech timber which 

 had been blazed by a land surveyor about twenty years before 

 and had accidentally been discovered during a re-survey of the 

 land. The blaze marks stoad out sharply, having been pro- 

 tected by gradual growth of new wood over them. Dr. Krout 

 stated that he had once seen a similar specimen. 



igoo. January 5. Dr. Miller, Acting President, and later 

 Provost C. C. Harrison, Honorary President, presided. 



Reports for session 1S99 were made by Dr. Miller, as Acting 



