Chapter XIV 



151 — 



The Vacuolar System 



these leaflets (Fig. 92) there are chondriosome-shaped vacuoles con- 

 taining a substance which, when preserved with mitochondrial 

 methods, becomes yellow, but which may be stained by iron haema- 

 toxylin and which, if the destaining is not carried far enough, ap- 

 pears black. This would make one think that these bodies corre- 

 spond to chondriosomes impregnated with anthocyanin. In reality, 

 as we were able to demonstrate by later work, they are vacuoles 

 containing tannin with which anthocyanin is associated. Now, 

 tannin, like the lipide substance of the chondriosomes, is rendered 

 insoluble with fixatives containing potassium bichromate, and 

 may be stained by iron haematoxylin. On the other hand, 

 the study of plants in which 

 anthocyanin is not associ- 

 ated with tannin, makes it 

 possible to observe that this 

 pigment is not preserved by 

 mitochondrial techniques and 

 that the young chondrio- 

 some-shaped vacuoles in 

 which pigment forms do not 

 stain with mitochondrial 

 methods. Therefore, Dan- 

 GEARD, instead of correcting 

 a partial error committed by 

 us, made the mistake of gen- 

 eralizing it. 



Let us examine in more de- 

 tail the development of the 

 vacuoles in the phanerogams. 

 In the barley root (Fig. 94), 

 for example, the phenomena 

 studied by Dangeard and 

 then by us, are particularly clear. If a very young root of a 

 seedling is studied in a solution of neutral red by crushing the root 

 gently, in such a way as to dissociate the cells without injuring 

 them, numerous minute elements are seen in all the cells of the 

 meristem. They are scattered about in the cytoplasm and are 

 stained deeply and homogeneously by the dye. In the very young- 

 est cells these elements are all small granules but they soon 

 elongate to undulous filaments which often afterwards anastomose 

 into a network. By their form and their dimensions these ele- 

 ments show a striking resemblance to the chondriosomes and an 

 observer not forewarned would easily take them for such. Never- 

 theless, they are distinguishable at first sight from the chondrio- 

 somes by a much greater diversity of appearance and by the fact 

 that they are reticulate. They seem to be composed of a very con- 

 centrated colloidal solution of semi-fluid consistency whose refrac- 

 tivity is such that they can easily be seen without vital staining. 

 In the course of cellular differentiation, it is observed that these 

 elements swell by absorbing water and then coalesce. They are of 



Fig. 95. — Young flower of Iris germanica. 

 Early stages in the development of the vacuolar 

 system in the trichomas of sepals. Vitally stained 

 with neutral red. 



