3 °6 
THE PLANT WORLD. 
disappears, the discharge of a misty vapor accompanying the 
change. 
By placing a coin heated to a proper temperature, on the frond, 
and exerting pressure, a green impression can be immediately 
produced. Metal stamps of various designs act similarly. To 
obtain printed impressions the letters require to stand out well. 
By playing a lens upon the frond for a short time, green spots 
or lines may be produced, accompanied by a beautiful demon¬ 
stration of the misty vapor making its escape. The changes 
thus produced are of course due to the vaporization of the 
brown coloring matter, thus leaving the chlorophyll unmasked. 
(Thomas Berwick. Proc. Bot. Soc. Edin. 22: 395. Jy. 1905.) 
“ . . . the leaves of the unifoliate species of Streptocarpus, 
e. g. S. Wendlandi, are superior objects for the demonstration 
of water-absorption by the leaf surface. If a wilted leaf is 
plunged under the surface of water, it will be quite quickly re¬ 
stored to a condition of turgidity.” (K. Goebel in Flora, 93: 
542. 1904.) 
A simple modification of Detmer’s experiment to demon¬ 
strate the need of light for photosynthesis is given by King in 
Torreya for April, 1905. Miss Haug (Bot. Gaz., November, 
1903) has called attention to a source of error in the experiments 
as described by Detmer, in which two pieces of cork are pinned 
opposite to each other on the two surfaces of the leaf. By this 
arrangement there is a possible exclusion of carbon-dioxide as 
well as of sunlight. The modification proposed by King is to 
substitute for the corks “ narrow strips of black cloth about as 
coarse-meshed as cheese-cloth.” By this means the carbon- 
dioxide finds ready access to the tissue by diffusion through the 
cloth, while light is effectually excluded. No starch is formed 
under the strips of cloth. C. S. G. 
