142 The Living Plant 



holding liquids in its meshes as a sponge might do, — a view more 

 prevalent formerly than now, even though it is sustained by the 

 appearance of the substance when killed and colored by dyes. 

 Others consider that protoplasm, aside from certain solid gran- 

 ules, is chiefly an emulsion of various liquids, which rest suspended 

 as tiny globes in a matrix of fluid ground substance, very much as 

 the tiny globules of oils remain suspended in water after violent 

 shaking of a mixture. And the advocates of this view, now in the 

 ascendant, have supported it by constructing, out of ordinary 

 chemicals, certain emulsions or foams, which show striking sim- 

 ilarities to living protoplasm not only in appearance, but in move- 

 ments, though they are, however, far enough removed from 

 protoplasm in all other respects. And a third view tries to har- 

 monize the two others by supposing that some protoplasm has 

 one structure and some the other. In one part only does proto- 

 plasm display a definite structure, and that is in the nucleus dur- 

 ing reproduction, a matter we shall presently consider. 



It may seem to the reader remarkable that I do not attempt to 

 illustrate so important a subject more fully by pictures. But 

 protoplasm in fact, because of the lack of clear definition in its 

 structure, is most difficult to represent well in any kind of pic- 

 ture. Indeed, hardly any two persons represent it alike, as 

 follows naturally enough from the fact that hardly any two per- 

 sons see it alike. In various figures in this book, however, I have 

 tried incidentally to give some, even though rather a conventional, 

 idea of its appearance, and to these figures (figures 33, 34, 39, 40, 

 41, 45) the reader will now find it worth while to refer. And I shall 

 at this point, add one more, and one of the best, in which the great 

 botanist Sachs has tried to represent it as if projected against 

 a black background, (figure 46). 



We come now to the important matter of the chemical com- 

 position of protoplasm, from which, in view of its many remark- 

 able powers, we naturally anticipate something of very unusual 

 interest. The most striking of the chemical facts about it, as the 



