CHAP, i The Cell 185 



is composed of both living and non-living matter, as well 

 as of water. 



Wiesner supported his view by experiments on dead and 

 old cell walls, in which, under the action of chlorine water 

 and other reagents provoking a gentle decomposition, 

 granular dermatosomes became visible. He brought for- 

 ward also in its support the presence of protein substances 

 in the cell walls of Fungi. On this hypothesis growth 

 takes place by the formation of new dermatosomes in the 

 protoplasm included in the substance of the wall. 



Wiesner's views called attention again to the question 

 of intussusception, and again acceptance of the process 

 became general, though not in the original form proposed 

 by Naegeli. Strasburger's observations as to lamination 

 from the exterior were confirmed by Noll's researches of 

 1887, in the course of which he was able to differentiate 

 the successive layers by delicate methods of staining. The 

 reassertion of the intercalation of substance by intussus- 

 ception was made in the case of structures like root-hairs 

 and fungal hyphae, by Haberlandt in 1889, an d by Zacharias 

 in 1891. The latter observer succeeded in introducing 

 a stain into the cell-membrane of a growing root-hair, 

 without stopping its growth, and found that the coloured 

 apex lost its stain during surface-growth, while the older 

 portions of the wall retained it. This could not have 

 taken place had the surface-growth been due, as Stras- 

 burger suggested, to a stretching of the thickening mem- 

 brane, but must have been caused by intercalation of new 

 particles. Other writers who supported this view were 

 Leitgeb (1884), Wffle (1886), Krabbe (1887), and Cramer 

 (1890). 



Strasburger's views were upheld not only by Noll, but 

 by Klebs in 1886, Wortmann in 1889, Zimmermann in 

 1887, and Askenasy in 1890. 



Pfeffer in 1892 tried to reconcile the opposing schools 



