172 The Anatomy of Plants BOOK n 



between them, causing them to range themselves alongside 

 one another. 



The most eminent supporter of this view was Altmann, 

 who wrote upon it in 1886-90. It led him to reject the 

 reticular theory entirely. He considered that the granules 

 constitute the living part of protoplasm, and that the fluid 

 in which they move is non-living. He called them con- 

 sequently bioplasts, so that a cell on this hypothesis became 

 not the unit of construction of the organism, but an assem- 

 blage or colony of bioplasts. 



This theory, though urged with considerable ingenuity, 

 met with but little acceptance. 



The views of Berthold have already been spoken of. In 

 1886 he put forward a fresh presentation of the fluid theory, 

 and taught that two fluids are concerned in the structure, 

 their relationship being that of the constituents of an 

 emulsion. He consequently abandoned the fibrillar or reti- 

 culate hypothesis, ascribing the appearances described as 

 such to optical rather than physical conditions. 



Berthold's work was followed in 1889 by Biitschli's foam 

 theory. On this view the finer reticular appearance of 

 protoplasm which can be observed under high magnifica- 

 tion is the optical expression of an extremely finely vacuo- 

 lated foam structure. Examination of very carefully pre- 

 pared artificial foams, made by rubbing up oil with potash, 

 or with solution of cane sugar, presented so remarkable 

 a similarity to the structure of protoplasm that they 

 were almost indistinguishable from the latter. Such 

 a structure presents under high powers of the micro- 

 scope a picture, not of droplets or bubbles pressed 

 tightly together, but of a network, the threads of which 

 are formed by the cross-sections of the thin walls of the 

 droplets as they are looked at in optical section. The 

 optical cross-section of a foam in fact is a network. 

 Suspended in the foam are numerous solid granules, these 



