CYTOPLASM AND ACTIVATION OF THE GENE 275 



only if the genes or whole chromosomes in question are present in 

 the homozygous condition, but in other cases also in the hetero- 

 zygous one. 



3. Very few, if any, cases are known in which this differential 

 action of the cytoplasm is found in crossing different varieties or 

 mutants of one species. But the cytoplasmic difference appears 

 rather frequently if subspecies and still more distant forms are 

 crossed. As far as evidence goes, it seems that its effect upon 

 the action of the genes increases with taxonomic distance. 



4. In one and the same case, not all gene-controlled characters 

 show the cytoplasmic influence. If we leave out of consideration 

 general actions of inhibition and also complete incompatibility, 

 it seems that such characters are most likely to be affected by 

 the cytoplasmic background, which are of a quantitative nature — 

 size of organs or parts, amount of pigment, shapes of parts, and 

 similar characters. 



It would be important to know whether or not specific prop- 

 erties of the cytoplasm exist (aside from the serological specifity) 

 that are different in forms with a cytoplasmic action of the type 

 just considered. Bellingshausen (1935) attacked this problem 

 in Michaelis' Epilobium material. The protoplasm of E. 

 luteum turned out to be more permeable to potassium chloride, 

 glycerin, and succinimide than hirsutum plasm. The permea- 

 bility for urea is decreased by chloral hydrate in a different way 

 in the two species, a fact that is accounted for by a different size 

 of pores and the presence of different lipoids in the two species. 

 These properties remained constant in 12 generations of back- 

 crosses and are therefore actually cytoplasmic. The interesting 

 observation of Michaelis (1935) belongs here, that E. luteum 

 is resistant to mildew; hirsutum, not; while luteum plasma with 

 hirsutum genom are almost resistent. This difference might, 

 of course, be of a serological order. 



D. The Theory of the Plasmon 



This last point now leads to the question whether or not we can 

 derive any generalization regarding the cytoplasmic action under 

 discussion. Apparently, some botanists are inclined to assume 

 that certain hereditary qualities may be transmitted by the 

 cytoplasm in the same way as other characters are determined 

 by the genes within the chromosomes (Winkler, 1923; Renner, 



