Chapter XV — 181 — Origin of Vacuoles 



proposed an hypothesis to explain the formation of vacuoles. This 

 hypothesis is based, on the one hand, on the fact that colloidal sub- 

 stances contained in the vacuoles are of very diverse constitutions, 

 and, on the other hand, on the fact that the cytoplasm is constantly 

 the locus of secretory phenomena (production of reserve or of 

 waste products) . The hypothesis assumes that among these prod- 

 ucts, those which are in a colloidal state separate by an unknown 

 physical-chemical mechanism from the cytoplasm in the form of 

 colloids non-miscible with the cytoplasmic colloids and composing 

 a distinct phase of the latter. They appear in the form of small 

 elements. These, by virtue of their semi-fluid consistency and of 

 their physical state, which is rather like that of the chondriosomes, 

 are subject to the same laws which determine the shape of the 

 chondriosomes. This explains the resemblance in form of these 

 two elements. According to our hypothesis, these colloids possess 

 a capacity for taking up water which is stronger than that of 

 the cytoplasm, and when the cytoplasm has reached its maximum 

 point of imbibition, the excess water is absorbed within these ele- 

 ments which are gradually transformed into a true solution and 

 constitute the vacuoles. In these vacuoles during the different 

 stages of their development, there may accumulate by absorption, 

 according to this theory, all the products secreted by the cytoplasm 

 which are capable of forming solutions or pseudosolutions within 

 the vacuoles. This hypothesis, which resembles that of Pfeffer, 

 would apply at least to a great number of cases but probably not 

 to all. 



The presence In some cells of several distinct categories of 

 vacuoles:- Recent research by Mangenot has drawn attention to 

 the existence of two distinct categories of vacuoles which are ob- 

 served in the mature cells of numerous plants. They were glimpsed 

 and very briefly cited some time ago by Went, Klercker and 

 Lloyd. Vacuoles which are rich in tannin, and very refractive, and 

 which reduce osmic acid instantly, are often observed in the same 

 cell side by side with, but in reality distinct from, other vacuoles 

 which do not contain tannin, are very slightly refractive and show 

 no reaction with osmic acid. The respective dimensions of each 

 are sometimes the same, or again the tannin-containing vacuoles 

 may be much more voluminous than the others, or conversely, may 

 be smaller, in which case they may appear as filaments or small 

 granules scattered in the cytoplasm around the vacuoles. Vital 

 dyes apparently stain these two categories differently. Cresyl blue, 

 for instance, stains the vacuoles containing tannin, blue or green, 

 and the other vacuoles, violet or rose. Cells with tannin-containing 

 vacuoles are very widespread in plants (Legumes, Mimosa, Ber- 

 beris, Eucalyptus, Oxalis, Monotropa, Hypopitys). 



These two categories of vacuoles, the one acid and rich in tan- 

 nins, the other without tannins and seeming to have a high pH, 

 Bailey has found in the cambial cells of gymnosperms and arbores- 



