Chapter X 



— 101 — Duality of the Ghondriome 



cells which we have studied and the chondriosomes of Saprolegnia 

 show exactly the same refractivity. Slightly superior to that of 

 cytoplasm, this refractivity, although very slight, still permits the 

 chondriosomes to be adequately seen. Under the ultramicroscope 

 the two categories of elements of epidermal cells and the chondrio- 

 somes of Saprolegnia are distinguishable only under very favorable 

 conditions. When visible, they always have the same appearance 

 and are seen only because of their very faintly luminous contours. 

 With the Zeiss micropolychromar they are made to appear very 

 clearly with a different color from that of the cytoplasm, green on 

 a red background, for instance, or yellow on violet. Chondriosomes 

 and plastids of epidermal cells, as well as the chondriosomes of 

 Saprolegnia, behave like extremely delicate elements which the 

 least change in osmotic equilibrium, or the 

 least pressure on the cover glass of a prep- 

 aration, suffices to change into vesicles 

 (cavulation). In a hypertonic medium they 

 keep changing shape as long as the cell is liv- 

 ing but as soon as it dies, they become 

 vesiculate (Fig. 67). 



We have already seen that in Saprolegnia 

 the chondrioconts are moved about slowly 

 by the cytoplasmic currents and that dur- 

 ing these displacements they change shape, 

 passing through the most varied forms. 

 They are even able to branch by growing 

 a kind of pseudopodium which afterwards 

 is retracted. In epidermal cells of tulip in 

 which cytoplasmic movements are very slow 

 or do not exist, nothing of this sort is ob- 

 served. In cells of Iris germanica and of 

 Allium Cepa, however, which are very favor- 

 able objects for study, we have observed for 

 the plastids these same displacements and 

 the same instability of form. (Figs. 68, 70, 

 150). During the movement from place to 

 place the plastids are capable of taking the 



most irregular shapes. They are capable of shortening by becom- 

 ing thicker or of elongating by stretching out. They may form 

 swellings along their long axes which are sometimes vesicular or 

 they may put out transitory ramifications which are later retracted. 

 Analogous observations have been made by Emberger for the leuco- 

 plasts in the epidermis of the bulb of Asphodelus cerasiferus. This 

 proves that the plastids and chondriosomes are composed of a semi- 

 fluid, very plastic substance, are in the same physical state and 

 possess the same viscosity. During these observations, moreover, 

 we could follow under the microscope, the process of division of 

 the chondriosomes in the leaf cells of Elodea canadensis, that of the 

 plastids in the epidermal cells of Allium Cepa and of the tulip, in 

 which the displacements of the plastids and the cavulation (vesicu- 



FiG. 69. — Cells from a 

 tuber of Fiearia ranuncu- 

 loides (A) before and (B) 

 after centrifuging. A, chon- 

 driosomes with and without 

 atarch dispersed in the cyto- 

 plasm; B, at one side of 

 the cell are found the nucleus 

 and the starch-bearing chon- 

 driosomes; those without 

 starch remain dispersed. 

 (After MiLOViDOV). 



