SUPPLEMENT 



ON NEW METHODS IN PHYSICAL 



CELL RESEARCH AND THEIR APPLICATION IN 



STUDIES OF POLLEN GRAINS AND SPORES 



BY 



B. M. AFZELIUS 



The rapid development in physical cell research has recently provided 

 much news of interest to pollen and spore morphology. Deeper understand- 

 ing of the cell, the morphology and composition of its organellae and their 

 finest constituents down to macromolecular dimensions can be gained 

 through the ever-widening application of refined techniques such as phase 

 contrast and polarization microscopy, ultra-violet light, interference, and 

 electron microscopy. Certain indirect methods are also of interest (e.g. 

 X-ray diffraction) and there are microscopical and other methods for 

 obtaining quantitative cytochemical data. Micrographs of macromolecules 

 can thus be made (cf. Wyckoff 1949, p. 189) and it is even possible (cf. e.g. 

 Frey-Wyssling 1954) to determine the macromolecular or particle weight 

 by microscopical methods. From a study of electron micrographs (Stein- 

 mann in Finean, Sjostrand, and Steinmann 1953) of the small spherical 

 particles constituting the lamellae of chloroplast grana Frey-Wyssling was 

 able to calculate their size as being equal to one to four Svedberg units, 

 containing eight to twelve chlorophyll molecules (the molecular weight of 

 one Swedberg unit = 17,600). Moreover, micrographs showing the exact 

 locahzation of enzymes in the cell are now available (Sheldon, Zetterqvist, 

 and Brandes 1955). By means of microscopical interferometric methods it 

 is, furthermore, possible to determine mass as small as 0.01 pg//<^ (Davies, 

 Engstrom, and Lindstrom 1953; 1 pg -- lO-^^ g). Microspectroscopical 

 methods allow of determination of mass as small as 0.001 pg (Caspersson 

 1950). 



To be able to make use of the new developments in the field of microscopy 

 it is often necessary to introduce new methods for preparing the material 

 to be studied. Thus the invention of the electron microscope (Knoll and 



