133 



absorption method and make comparisons with interferometric ones. Using 

 the X-ray technique measurements of 0.1 pg//^^ can be made. 'Fhe Dyson 

 interference microscope provides measurements one order of magnitude 

 greater (Davies et al. 1953), that is 0.01 pg//t". Inirthermore, it is possible 

 to apply the interference microscope in investigations of living material. 

 G. Bahr (1957) has succeeded in using the electron microscope for quanti- 

 tative cytochemical measurements. As an example it may be mentioned 

 that his calculation of the weight of a single microsome gives an approximate 

 value of 8 to 16 X IQ-ia g. 



General methodological problems 



There is no longer a tendency to separate form and function but to try to 

 coordinate understanding of both in order to obtain an integrated picture 

 of the living cell. It is, however, not an easy task to evaluate data obtained 

 by different direct and indirect methods and to combine them to form a 

 conception of the cell. It must also be borne in mind that different results 

 are occasionally obtained even when applying the same technique to iden- 

 tical material. Likewise certain EMG:s may be interpreted in different 

 ways by different workers etc. To my mind no purpose is served in trying 

 to reconcile results and interpretations which do not fit; at the present 

 state of knowledge and technique it is better to accept and acknowledge 

 the divergences. But such problems, especially those arising from differences 

 in interpretations, lead beyond the more particular problems of our field 

 into those of a more methodological/epistemological character. 



REFERENCES 



Afzelius, B. M. 1955. On the fine structure of the pollen wall in Clivia miniata. Bol. Not. 108. 



1956. Electron microscope investigations into exinc stratification. Grana palynologica I: 2. 



Bahr, G. F. 1957. Changes in liver cell elements during stimulated protein synthesis. Stockholm. 



(Thesis.) 

 Bradley, D. E. 1954. Evaporated carbon films for use in electron microscopy. Brit. J. Appl. 

 Phys. 5: 65. 



1957. Some botanical applications of the carbon replica technique. Proceed. 1st European 



regional conference on electron microscopy, Stockholm. 



Burton, E. F. 1946. The electron microscope. New York. 



Gaspersson, T. O. 1950. Cell growth and cell function. A cytochemical study. New York. 



Dahl, O. and Engstrom, A. 1954. X-ray analysis of mass of pollen grains. Huitiemc Congres 

 international de Botanique. Bapports et Communications, Section 6. 



Davies, H. G., Engstrom, A., and Lindstrom, B. 1953. A comparison between the X-ray ab- 

 sorption and optical interference methods for the mass determination of biological structures. 

 Nature, Lond. 172, p. 1041. 



Davies, H. G., Wilkins, M. H. F., Chayen, J., and La Cour, L. F. 1954. The use of the inter- 

 ference microscope to determine dry mass in living cells and as a quantitative cytochemical 

 method. Quart. J. Micr. Sci. 95: 3. 



