surface, that in direct contact with the vacuolar sap, was also in 

 an active state of flow. It was this streaming interfacial proto- 

 plasm which caused movement of the vacuolar sap and the particle 

 within it. There was therefore no quiet layer between protoplasm 

 and sap, which meant to my student that there was no tonoplast. 

 He failed to appreciate that the tonoplast and cell membranes in 

 general are not inert skins but a surface layer of living proto- 

 plasm. The tonoplast is protoplasm ; in that sense is it formed of 

 a substance immiscible with water. It is, as Hugo de Vries said, 

 "a membrane differentiated and living". 



Much of the misunderstanding in regard to protoplasm arises 

 from a failure to realize that protoplasm possesses both liquid and 

 solid properties. Its liquid character is real but superficial. Its 

 solid qualities are basic. That protoplasm is liquid is evident 

 from the fact that it flows, but it is in no way comparable to a 

 solution of salt in water. Viewing protoplasm as a liquid devoid 

 of solid properties was an excusable fault in the classical cytolo- 

 gists, but the modern physiologist is aware, as is GuiLLiERMOND, 

 of the true physical nature of living matter and the need of struc- 

 tural continuity. GuiLLlERMOND refers to this indirectly by attrib- 

 uting to protoplasm such properties as torsion, elasticity, and 

 immiscibility in water. Warren Lewis once expressed the need of 

 structural continuity in protoplasm when he stated that were it 

 not for the glutinous qualities, the tackiness of protoplasm, we 

 should all fall to pieces. In short, protoplasm holds together, and 

 this is as true of fluid protoplasm as of firm protoplasm. 



GuiLLlERMOND concludes this book with the statement that the 

 future of cytology lies in the union of morphology and physiology. 

 In return for the admission by a morphologist that anatomy with- 

 out physiology is sterile, let me say to Professor GuiLLlERMOND 

 that physiology is meaningless unless supported by structure and 

 function. 



The present volume is the first addition, printed in the New 

 World, to the list of books which Dr. Frans Verdoorn is editing 

 and publishing under the title of "A New Series of Plant Science 

 Books". The book was especially written for the "New Series" by 

 Professor A. GuiLLlERMOND ; it is the translation of an unpublished 

 French manuscript and not merely an English version of a previous 

 book by Guilliermond. 



The translator is Mrs. Atkinson of Amherst, Massachusetts 

 (Ph.D. University of Wisconsin, sometime C.R.B. Fellow in Bot- 

 any, University of Louvain). Mrs. Atkinson has given us far 

 more than a translation of the original manuscript, for there was 

 much interpretation and rearrangement to be done. The translator 

 is to be congratulated on accomplishing a difficult piece of work 

 so well. Valuable help in editing the Ms. was also rendered by 

 Dr. J. DUFRENOY of Louisiana State University. 



September 194-1 



William Seifriz 



