Pennsylvania for Sessions 1899-1900. XXV 
Professor Marsh. Microscopic sections, showing the struc- 
ture of the organism, were exhibited and described. 
December 15. 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 
close agreement between the dates for flowering, fruiting and 
autumnal leaf coloring, as recorded by different observers. 
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 stoed 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. 
zgoo0. January 5. Dr. Miller, Acting President, and later 
Provost C. C. Harrison, Honorary President, presided. 
Reports for session 1899 were made by Dr. Miller, as Acting 
