THE PLANT-CELL 37 



the structure of living protoplasm, the conclusions of different ob- 

 servers are so conflicting that none of them can be accepted without 

 qualification. 1 While it is by no means clear that the protoplasm 

 always has the same structure, it is certain that sometimes, at least, 

 it shows a fine honeycombed or foamy appearance. A very similar 

 appearance is exhibited by placing a small particle of a paste com- 

 pounded of finely rubbed olive oil and potassium carbonate in contact 

 with a drop of water. A fine emulsion is thus produced, which 

 under the microscope presents a remarkable resemblance to the 

 structure of living protoplasm. This has led the discoverer of this 

 fact, Butschli, to the conclusion that the protoplasm is really com- 

 posed of a similar structure, the living portion occupying the walls 

 surrounding the cavities, which contain a more fluid substance. The 

 recent studies of Wilson (13) confirm in general Butschli's conclu- 

 sions, although modifying them in certain respects. 



While the protoplasm is never strictly a liquid, the degree of 

 cohesion of its particles varies much in different cases. Thus the 

 outer ectoplasm or hyaloplasm is more coherent than the inner gran- 

 ular plasma, but it is itself subject to differences which have been 

 compared to those taking place in gelatine when it is alternately 

 warmed and cooled. The coherence of cilia and fine pseudopodia is 

 very great. Where the protoplasm occurs in small naked masses, it 

 tends to assume a globular or oval form, due to the strong surface 

 tension. 



While we are accustomed to speak of protoplasm as if it were a 

 definite substance, and we cannot recognize any visible difference 

 between the protoplasm of different organisms, it is evident that 

 important inherent differences must exist. The ovum of a Fern, 

 although closely resembling that of a Moss, "could not be conceived 

 as developing into anything but a Fern. There must be some 

 essential peculiarities of the components of the protoplasm which 

 determine that the naked protoplast shall become a Fern and not a 

 Moss. 



The Ultimate Structure of Protoplasm 



It is not at all likely that any of the visible structures observed in 

 the protoplasm really represent its ultimate component parts. It 

 seems much more probable that the real protoplasmic units "Pan- 

 gens," " Biophores " are much too minute to be visible to any lenses 

 which we now possess. These protoplasmic units are not necessarily 

 similar in composition, and may perhaps be of many kinds. They 

 are supposed to be capable of arrangement in a great variety of ways, 

 comparable to the different arrangements of the atoms in the so- 



1 For a full discussion of the more important theories see Fischer (3) . 



