THE AUSTRALIAN NATURALIST. 119 
Apologies for absence from the President and Mr. E. 
Cheel were read. Master Horan was elected to member- 
ship. 
Miss Agnes Brewster gave an excellent lecturette on 
“Some Native Plants and Their Visitors,’’ illustrating her 
remarks on pollination by very clear sketches. Mr. L. 
Gallard exhibited a further series of wasps parasitic on 
Longicorn beetles and on Fruit Flies. Mr. H. E. Finckh, 
the large bean of Poinciana regia, and a fruit of Kigelia 
pinnata, the latter being used medicinally in rheumatic 
complaints. Mr. A. A. Hamilton, Siebera Stephensonii, 
Bauera capitata, Oxylobium cordifolium, and Pulingia her- 
manniaefolia, rare shrubs, collected near Botany Bay; also 
a series of ferns representing New South Wales forms of 
Aspidium, with notes. 
THE PHYSICAL SIDE OF OSMOSIS. 
(SUMMARY.) 
By F. W. Carpenter. 
The earliest physical experiments on Osmotic Pres- 
sure were performed with a view to imitating the action 
of plant cells, more especially those in the root in which 
osmosis takes place. After many failures, artificial mem- 
branes made of copper ferrocyanide, supported on the 
porous structure of an unglazed earthenware pot, were 
found to give satisfactory results. With increased care 
in the construction of these colloidal membranes of cop- 
per ferrocyanide, it was found that the best membranes 
are impervious to dissolved substances, whilst they allow 
the free passage of water. Such membranes act like a 
very perfect filter or sieve, which is able to prevent the 
passage of all but the very smallest molecules. It is easy 
to make membranes which are impervious only to the 
larger molecules, such as those of sugar, or of the other 
substances occurring in the sap of plants. 
Experiments were shown in which the root pressure 
of the plant was imitated by immersing a prepared cell 
containing sugar solution, in a vessel of pure water. In 
the living plant the sap plays the same part as the sugar 
in our experiments; and a continuous flow of water can 
be maintained from the soil through the roots to the plant. 
