The Cytoplasm as Specific Substrate 233 



is no reason why in green-yellow variegation, involving diflFerent 

 chemical processes of chlorophyll synthesis, transitions between the 

 green and yellow product should not be possible, dependent upon any 

 type of environmental effect which may include the position of the 

 first cells in the whole. Correns possibly thought of such an inter- 

 pretation when he said that the features in maize are caused by the 

 structure of grasses and therefore are not of genetic importance. I 

 realize that the difference between the explanation of some special 

 features in terms of plasmagenes and that in terms of physiological 

 processes involves a difference in basic thinking, as I have tried to 

 show for a number of examples in different fields of genetics (Gold- 

 schmidt, 1954). 



Thus I like to conclude that the facts relating to status albo- 

 maculatus in plants demonstrate another example of cytoplasmic, 

 hereditary differences of the substrate type, which, however, are not 

 collaborating with or modifying genically controlled reactions but are 

 affecting chemical processes within an autonomous inclusion of the 

 cytoplasm, the plastids. In an inquiry into the genetic properties of the 

 plastids, the facts show only that the function of the plastids is de- 

 pendent on the surrounding cytoplasm, which after all is not surprising, 

 even if they are autonomous in regard to duplication. 



It should be added that Renner (1922ff.), who analyzed cases in 

 Oenothera with undoubted genetic differences of plastids which can 

 be sorted out, thinks that Correns' experiments might be explained on 

 the basis of plastid differences as opposed to cytoplasmic ones. Renner's 

 analysis will be discussed in the following sections. Here it may be 

 stated that Correns, Wettstein, Noack, and Rhoades agree that some 

 facts may be explained best in Correns' way by a labile cytoplasm af- 

 fecting plastid function. Renner, however, thinks that in all cases ge- 

 netically different plastids and their sorting out may be involved, and 

 Wettstein (in Correns, 1937) accepts this, at least for a majority of 

 cases. But there are also claims by Noack that within the same material 

 both types occur simultaneously. In the remarkable material of Anders- 

 son-Kotto (1930) in ferns, the experimental facts are so complicated 

 that it is hardly possible to explain them in one or the other way. The 

 present discussion does not intend to analyze the problem of plant 

 variegation. We are interested only in knowing whether the genetic 

 behavior of the plastids may be taken as a proof for the existence of 

 plasmagenes and, generally, what their behavior means for the prob- 

 lems of cytoplasmic inheritance. 



