I CYTOPLASM 195 



cell wall, on the contrary, vital staining is much less easily obtained. 

 According to Strugger's investigations (193 5/1936) on vital staining, 

 the Ph of the surrounding liquid is the main factor in dyeing; this is 

 true not only in the living state, but according to Pischinger (1937), 

 Drawert (1937) and others also in fixed protoplasts. According to 

 the theory of junctions this means that the acid and basic groups of 

 the framework, which are screened off in the I.E. P., must first be 

 liberated by slight hydrolysis in order to be capable of reacting with 

 the dyestuff. 



The vacuoles owe their existence to substances which are tempo- 

 rarily or definitively excluded from interaction with the framework 

 of the cytoplasm. For this reason these sap-filled spaces represent 

 places in which excretory (definitive elimination) or reserve substances 

 (temporary elimination) are stored. All cell sap components like 

 anthocyanins, tannins, glucosides, etc. must therefore be regarded as 

 substances eliminated from the cytoplasm. Hence the vacuoles are 

 primarily excretory organelles in which all kinds of substances that are 

 inconsistent with the cytoplastic molecular structure are stored; their 

 function of regulating osmotic phenomena is only a secondary task. 



Lipidic drops. As in the case of water, there is an upper limit to the 

 amount of molecularly dispersed lipids bound by the cytoplasm 

 structure. Beyond this limit the Hpid molecules cluster together into 

 globules which represent an analogy to the vacuoles; they might be 

 called lipidic vacuoles as counterpart to the aqueous vacuoles. Apart 

 from the surface films at the phase boundaries, as a rule neither the 

 lipidic drops nor the vacuoles possess a structure. Their content is 

 semi-solid to liquid, optically isotropic and homogeneous in the 

 physico-chemical sense. 



These regions, which are homogeneous and therefore foreign to 

 the protoplasm, are usually regarded as reserves for the metabolic 

 process. In this connection we think in the first place of oil and fat 

 containing seeds, which mobilize their lipids during germination. 

 However, we also find lipidic secretions of an irreversible nature, 

 which can scarcely be considered as reserve substance (fatty de- 

 generation, lipophanerosis). 



A.leurom grains . The accumulation of proteins in the cytoplasm leads 

 to two types of differentiation. On the one hand, easily soluble 

 proteins with globular molecules of relatively low molecular weight 



