Chapter X — 111 — Duality of the Ghondriome 



the archegonium is formed from an initial cell containing only 

 chondriosomes and he finds that the egg also lacks chloroplasts. 

 These facts make it seem extremely probable that, at some stages 

 in development in the bryophytes, the chloroplasts are capable of 

 regression and of taking on mitochondrial form just as in the 

 pteridophytes and in certain algae. 



However this may be, it follows from data presented for the 

 first time in the splendid work of Emberger and Mangenot, that 

 the chloroplasts may, under some conditions, lose their chlorophyll, 

 become considerably smaller, and take on again the size and shape 

 of typical chondriosomes. The form typical of chondriosomes and 

 the form typical of chloroplasts are therefore reversible and the 

 chloroplasts may be considered as chondriosomes containing chlo- 

 rophyll. The chloroplast is derived from a chondriosome and may 

 under certain conditions lose its chlorophyll and revert to the 

 state of the chondriosome, the state which is characteristic of the 

 functionally inactive phase of plastids, exactly as the amyloplast 

 resumes its initial form after the absorption of its starch. If this 

 reversibility of chloroplasts is not ordinarily observed in phanero- 

 gams, it is doubtless because, according to the research just dis- 

 cussed, the chlorophyll-containing tissues in these plants achieve 

 a state of differentiation too advanced for a regression to take 

 place such as occurs in plants less evolved. 



Therefore the fact that chlorophyll is elaborated in a continuous 

 or discontinuous manner influences very notably the appearance 

 taken by the chondriome in chlorophyll-containing plants. In the 

 first case, the cells contain constantly and at the same time, both 

 large chloroplasts and small chondriosomes ; in the second case, on 

 the contrary, there are found, during the periods when chlorophyll 

 is lacking, chondriosomes which all together constitute a chondri- 

 ome analogous to that encountered in cells of animals and fungi, 

 and in which it is not possible to distinguish the plastids from the 

 genuine chondriosomes, and it is only during phases of elabora- 

 tion of chlorophyll that some of the chondriomal elements grow 

 and become large chloroplasts. 



These facts will be illustrated by a study of saprophytic or 

 parasitic phanerogams in which chlorophyll is formed only in very 

 small quantities or, in some species, not at all. Among these, 

 Limodorum, a saprophyte which is poor in chlorophyll, contains 

 only very small chloroplasts. In the genus, Orobanche, in which 

 chlorophyll has disappeared, plastids elaborating starch are still 

 observable which in some portions of the plant also contain carotin- 

 oid pigments. In the stem of Monotropa, in which chlorophyll is 

 also lacking, there is no longer production of starch, except in 

 the endodermis, and in that region only, can the plastids be dis- 

 tinguished from the chondriosomes. This distinction is impossible 

 in the tissues of Cytinus Hypocistis, a plant more completely 

 adapted to parasitic life. This plant is also lacking in chlorophyll 

 and has lost its power of forming starch (Emberger and Mange- 

 not, unpublished observations). 



