8 THE MOLECULAR ARCHITECTURE OF PLANT CELL WALLS 



1873 supported this latter view. The real study of pectic compounds 

 begins, however, with Mangin (1892, 1893) who laid the foundation of 

 our present ideas. He showed that there are two series of compounds 

 — acid and neutral — each with several members differing in solubility, 

 and succeeded in demonstrating that all these differed considerably 

 from cellulose in the chemical sense. He showed further that hardly any 

 plant tissue is free of pectin, which normally is associated intimately 

 with the coexistent cellulose but only mechanically and not chemically. 

 He confirmed the earlier view of Payen that the middle lamella contains 

 calcium pectate and opposed successfully the ideas of Strasburger by 

 claiming that this is a true intermediate layer. Through the work of 

 Mangin, and of many others both botanists and chemists, the next 

 twenty years produced much valuable data on the types and distribution 

 of these compounds, but these later developments, as well as the modern 

 treatment of the micellar theory, are best summarized in the body of the 

 book. 



This remarkably rapid development in the field of carbohydrate 

 biochemistry and biophysics was naturally paralleled by a similar 

 expansion in our knowledge of protoplasm. Up to about 1864 this 

 remarkable substance had been conceived as a viscid, slimy liquid 

 containing granules, though Brucke had concluded that such an appear- 

 ance must cover some kind of organization. This fluid theory, with 

 modifications, was in fact held by de Bary, Schwendener and even 

 Ndgeli up to about 1877, when some botanists {e.g. Volten, 1873-6) 

 and zoologists (notably Schuhe (1871) and later Flemming (1882)) were 

 beginning to accept the evidence for the alternative fibrillar structure 

 of protoplasm then coming into favour. Here we meet again the con- 

 stantly recurring insistence on the fundamentally fibrillar organization 

 of biological substances. An attempt to harmonize the Granular and 

 the Fibrillar Hypotheses, largely at the hands of Fromman (1867), led to 

 the conception of protoplasm as fundamentally a network in which the 

 nodal points in the net could give the erroneous impression of granules. 

 This was the so-called Reticular Hypothesis, modified later by Butschli, 

 who interpreted the reticular appearance as the optical expression of a 

 foam structure and proposed the Honeycomb Theory associated with 

 his name. At this time the Reticular Hypothesis in particular received 

 very strong support, though Pfeffer in 1890 sounded a warning note in 

 denying that protoplasm could be such a firm, continuous and per- 

 manently rigid structure as it was apparently coming to be. Again, 

 Schwartz (1887) pointed out that a reticulate appearance, identical with 

 that said to be visible in protoplasm, could be induced in the white of 



