12 PROCEEDINGS OF THE ACADEMY OF 



divides into two, four, &c., cells, so that in the filament a number of cells lie side 

 by side, and from this compound filament the large matured trichoma is formed 

 by a continuation of growth and division. The zoospores are formed only in the 

 younger fronds, these old compound trichomata appearing to be incapable of 

 developing them. The endochrome in a cell about to produce zoospores 

 divides into several more or less irregularly globular or pyriform masses. This 

 change takes place almost simultaneously in a number of consecutive cells. The 

 walls of the cells now undergo some alteration, whereby they become soluble 

 in water. And as the division of the endochrome occurs first in the most 

 distant cells of the filaments, so does also this change in the cellulose coats. 

 Solution of the walls now takes place, the partitions between the cells disap- 

 pearing, and the outer walls opening out, separating from one another. At the 

 same time the zoospores begin to move uneasily, rolling on themselves, pushing 

 forward, &c., and soon make their exit in a long stream which issues from the 

 end of the filament. 



This plant appears to be the same as tliat described by Kiitzing under the 

 name Schizomeris Leibleinei. No European observer has, however, as yet 

 noticed the manner in which the latter produces its zoospores, and therefore it 

 is impossible to be certain in the identification. US. Leibleinei should be Ibund 

 to differ essentially in the mode of giving birth to zoospores from the Ameri- 

 can species, the latter will form the type of a new genus. 



For the present it seems better, however, to consider the two identical. 



Jiio. Tomes, F. R. S., London, was chosen a corresponding 

 member of the Department. 



Nov. 2d, 1868. 

 Mr. Chas. Bullock in the Chair. 

 Twenty-six members present. 



Mr. T. W. Starr presented to the Department twelve slides, illus- 

 trating the anatomy of miscellaneous insects, among which is the 

 seventeen-year locust. 



Nov. l^ith, 1868. 

 Director, Wm. Pepper, M. D., in the Chair. 



Twenty-six members present. 



Mr. W. H. Walmsley donated twelve slides illustrating vegetable 

 structure. 



Dr. F. W. Lewis donated slides of miscellaneous objects. 



Dr. Wood exhibited to the Department fruiting specimens of a fresh-water 

 Alga, which he had found near Chelten Hills, Montgomery County, growing in 

 a rapidly flowing creek, on stones, which it covered more or less completely 

 with a dark purplish, mucous coating. He stated that it might be referred, 

 with some doubt, to the European plant, Chaniransia chah/bea, from which it 

 differs, however, in its habit of growth, as well as in the filaments being much 

 thicker and nearly twice as long. He gave the measurements of the oval 

 spores as about 37^50 ii the transverse, by ^^'qq in the long diameter. The 

 diameter of the filaments is about the ^sV)^ ^^ '^'^ inch. 



The doctor also exhibited specimens of a new species of Palmella, collected 

 on the banks of the Schuylkill above Manayunk, which grew on the faces of 

 rocks, kept constantly wet by dripping spring water. He proposed for the 

 plant the name of Palmella Jesseni, after Prof. Jessen, of Prussia, and gave the 

 following specific description of P. Jesseni, n. sp. 



P. thallo expanse, initio dilute aut late viride, molle, pellucidulo, a?tate 



