Chapter IX 



THE RELATIONSHIP BETWEEN 

 CHONDRIOSOMES AND PLASTIDS 



Interpretations:- It was logical to admit from the facts already 

 displayed, which have been verified by many observers, that the 

 plastids described by Schimper arise by differentiation of some of 

 the elements of the chondriome during cellular development. This 

 opinion, which had been maintained from the beginning by many 

 workers, notably Pensa (1910), Lewitsky (1912-1913), Foren- 

 BACHER (1912), Maximov (1913), and which we ourselves were 

 among the first to formulate in our early work, is still held by 

 Lewitsky and his school (1925-1927), Alvarado (1918-1925), 

 MoTTE (1928), Gatenby and his collaborators (1930), Jutta VON 

 Loui (1930), Chalaud (1923), Lewis Anderson and others. It 

 was adopted by Wilson in his book, The Cell in Development and 

 Heredity (1925). Still the opinion has been variously expressed. 

 Thus, for certain investigators such as Lewitsky and Randolph, 

 the chondriosomes are not permanent components of the cytoplasm 

 but form de novo from it. Our first interpretation was quite con- 

 trary to this. Not having recorded any fact which would permit 

 us to think that the chondriosomes can arise by differentiation 

 from the cytoplasm, we had from the beginning considered them 

 as permanent components of the cell, incapable of forming other- 

 wise than by division of pre-existing chondriosomes. Therefore 

 at that time, we considered the plastids of the phanerogams as a 

 variety of chondriosome, differentiated in the course of cellular 

 development and having a special function. The plastids, there- 

 fore, we believed belonged to a much more general category 

 present in every cell, whether plant or animal. Then too, the 

 theory that we had formulated was only an extension of that of 

 Schimper and Meyer and in no way contradicted it. It is this 

 same point of view which Meves and Alvarado adopted. 



Although based on incontestable facts, this theory, however, 

 raises very serious theoretical difficulties, for it can only be applied 

 to higher plants. In fact, although in the phanerogams the origin 

 of plastids had been for a long time only imperfectly known, this 

 was not so for the algae. In many of these plants, as has already 

 been said, the chlorophyll is present in all stages of plant develop- 

 ment and in that case chloroplasts are observed in all cells. These 

 chloroplasts are transmitted by division from cell to cell, beginning 

 with the egg. This has been well known since the work of Schmitz. 

 We have seen, besides, that in many algae there is in each cell 

 only a single, voluminous chloroplast which divides at each cellular 

 division. This chloroplast, however, can not be considered as 

 different from the chloroplasts of the phanerogams, for it offers 

 the same histochemical characteristics. There are found, more- 



