Chapter X — 107 — Duality of the Ghondriome 



Analogous phenomena were found later (Cholodny, 1923) in 

 the submerged leaves of Salvinia natans which, as is known, look 

 like roots, as they have no chlorophyll and are reduced to veins. 

 The chloroplasts which are present at first in these leaves lose their 

 chlorophyll and take on the appearance of chondriosomes abso- 

 lutely indistinguishable from the genuine chondriosomes. 



Investigating the Selaginellas (Figs. 75, 76), Emberger ob- 

 served that in cells of the meristem and in the spores where the 

 chondriome contains above all long chondrioconts, there is only a 

 single colorless plastid, which also appears as a chondriocont but is 

 a little larger than the others and is pressed against the nucleus. 

 This organelle, already pointed out by Haberlandt, Sapehin and 

 P. A. Dangeard, which is at first scarcely distinct from the other 

 chondrioconts, grows little by little during cellular differentiation 

 until in each cell of the leaf and stem there is a single chloroplast. 

 It is composed of a series of large swellings united by thin filament- 

 ous portions which are brought about by uncompleted divisions of 

 the initial plastid. This fact is particularly interesting from two 

 points of view. First, in Selaginella and Anthoceros (in which 

 there is also in each cell only one chloroplast, crescent-shaped in 

 this case, more or less appressed to the nucleus but always larger 

 than the small colorless plastids of embryonic cells of Selaginella) , 

 there are found the intermediate steps between the plastids of the 

 phanerogams and the large chloroplasts of some algae. This shows 

 that there is no reason to consider the chloroplasts of the algae as 

 different from ordinary plastids. Secondly, the presence of this 

 solitary plastid, which can be followed through all cells of Selagi- 

 nella and which divides when the cell does, furnishes undeniable 

 proof that the plastids maintain their individuality during the 

 course of cellular development and arise always from the division 

 of pre-existing plastids. The behavior of the plastids in the phaner- 

 ogams makes this seem likely but does not sufficiently demonstrate 

 it. 



The investigations of Mangenot (1922) brought out that the 

 algae behave differently, from the- point of view of plastidial de- 

 velopment, depending on whether the chlorophyll persists in all 

 stages of development or disappears in the sexual organs. When 

 it persists, the plastids are distinguished from the chondriosomes 

 in all stages of development, including the egg, by their size, their 

 shapes and their colors. Consequently chloroplasts and chondrio- 

 somes are coexistent at all times. 



Mangenot demonstrated the presence of large chloroplasts and 

 small chondriosomes at all stages in the Siphonales. These 

 had already been encountered in Vaucheria by Rudolph. These 

 two categories of organelles, in spite of the difference in their 

 dimensions, have analogous shapes and divide at the same time 

 in some phases of development. Such is also the case in the 

 Fucaceae, in which, however, the chlorophyll and fucoxanthin lose 

 their intensity in the oogonium and in the apical cells. There the 

 phaeoplasts take on the form of small rod, or spindle-shaped 



