Botany. — “A new method of recording the modifications in 
aperture of stomata.” (First Communication). By M. Pinknor. 
(Communicated by Prof. F. A. F. C. Went). 
(Communicated at the meeting of October 30, 1920). 
§ 1. Zntroduction. 
For organisms which, like the “higher” plants, live as a rule in 
the (gaseous) atmosphere, the regulation of the gas interchange is an 
essential point in the organisation. In connection with this the fact 
must be pointed out, that among the vegetative organs, common to 
all plants, the only part that is capable of quick response in con- 
sequence of its specialised structure, and thus deserves the name of 
“apparatus”, is the very part that has to regulate the gas interchange. 
This organ is the stoma (Spaltöffnungsapparat). 
Just as essential as the stomata themselves are for the plant, the 
study of them is for the plant-physiologist. The finding of methods 
to get acquainted with the behaviour of stomata by means of expe- 
rimental researches, has been indeed a subject of constant care in 
physiology. Much has already been done in this department, but 
of course there are always improvements to be made and as an 
attempt in that direction should be regarded the conception of a 
self-recording type of an existing apparatus treated below. 
After the exhaustive discussion, which van SrLOGTEREN, in the 
introduction to his dissertation ') has devoted to the numerous direct 
and indirect methods, invented to judge the aperture of stomata — 
I think it to be superfluous to mention these methods again and I 
restrict myself to quoting what vaN SLOGTEREN says about the poro- 
meter-method of Darwin and Perrz and its advantages. *) 
“... it is based on the following principle: a glass chamber is 
fixed air-tight to a leaf and through a tube connected with this 
chamber, the air is sucked out, so that the pressure in the chamber 
is diminished. After the side-tube has been closed, the difference in 
pressure inside and outside the chamber, can only be annulled, 
when air is sucked through the leaf. From the time, necessary for 
making equal the pressure, the degree of aperture of the stomata 
is judged. 
1) E v. SLtoareren, De gasbeweging door het blad in verband met stomata en 
intercellulaire ruimten. Groningen 1917, p. 1 —13. 
2) Le, pal. 
