366 BOTANICAL GAZETTE [November 







as being respectively in the gel or sol state. It is the intermediate 

 degrees of viscosity of protoplasm of whose physical structure and 

 therefore- colloidal state we are totally ignorant. Extremely vis- 

 cous protoplasm (v.v. 8) is probably a gel, but whether very viscous 

 or decidedly viscous protoplasm is cannot be conclusively stated. 

 This matter may not appear to be a serious one at first, but a r 



brief consideration of the indiscriminate use of the term gel in the 

 literature will show the misinterpretations to which such usage 

 leads. 



Bayliss (2) states: "There is one fact about which there can 

 be no doubt, that is, that protoplasm behaves as a liquid"; while 

 Mathews (19) states that protoplasm "is a jelly-like substance or 

 technically a gel." An older investigator (Rhumbler 22), during 

 a discussion on the structure of protoplasm, says that "protoplasm 

 cannot be a solid substance," while a recent workei (Hyman 13) says, 

 the fact "that isolated pieces of protoplasm assume 1 he spherical form 

 is not necessarily a proof of its fluid condition," and that "proto- 

 plasm is in the gel state." Each of these statements is supported by 

 some experimental facts, but each is true only in part. Protoplasm 

 does not always behave as a liquid (the highly viscous, quiescent 

 protoplasm of bread mold, for example), nor is it always a gel 

 (as for example the very liquid endoplasm of Euplotes). Kite 

 (15) has well expressed the exact state of affairs as follows: "Living 

 matter occupies an intermediate position betw r een true solids and 

 true liquids and has many of the properties of both as well as 

 properties peculiar to itself. It belongs to the class of colloids 

 known as emulsoids and exists in either a gel (hydrogel) or a sol 

 (hydrosol) state." Unfortunately, however, Kite then proceeds 

 N to use gel as descriptive of protoplasm regardless of viscosity. To 

 be sure, viscosity is not a precise index of physical structure, but 

 with ordinary illumination we have no other criterion by which 

 to judge the exact colloidal state of protoplasm, and a low viscosity 

 is strongly suggestive of a sol, or at least does not suggest a gel 

 state. Such statements as "The living endoplasmic substance is 

 a very dilute and apparently homogeneous gel," and "This struc- 

 ture (the jelly surrounding the egg of Asterias) has a low viscosity 

 for a gel and is therefore extremely dilute," are inexact and can 



