I CARBOHYDRATES, CHITIN AND CUTIN 507 



Vegetable cellulose membranes were studied (Frey-Wyssling, 

 1 941) with the object of discovering whether in laminated systems 

 the individual layers are of parallel texture, or whether it is a matter 

 of interweaving. We have examples, such as the algae \^alonia (Van 

 Iterson, 1933; Preston, Nicolai, Reed and Millard, 1948) and 

 Chaetotnorpha (Nicolai and Frey-Wyssling, 1938), the laminated cell 

 walls ot which can be split up into single lamellae of a few tenths of 

 a // in thickness ; these lamellae are made up of strictly parallel fibrillae, 

 which accounts for their striking cleavability parallel to the fibre 

 direction. In consecutive lamellae the fibre directions cross at approxi- 

 mately right angles (in 'Valonia at 78°); consequently the optical 

 anisotropy of the individual lamellae is to a large extent mutually 

 neutralized and, in transmitted light, the appearance is roughly that 

 ofstatistically isotropic packets of layers. (Cf. Preston, 1947; Picken, 

 Pryor and Swann, 1947). 



As opposed to these systems of membranes with uniform parallel 

 texture of the individual lamellae, we have the fine-structure of the 

 primary wall of cotton fibres. This thin membrane exhibits, according 

 to Anderson and Kerr (1938), three different systems of striations, 

 one of which runs perpendicular to the fibre axis, the two others 

 falhng symmetrically at an angle of about 30° obliquely from the left 

 and right. As the membrane cannot in this case be split up into three 

 lamellae, presumably there are three different fibrillar directions in one 

 and the same lamella. It may be supposed that submicroscopic fibriUae 

 are interwoven in the three directions after the manner of a textile 

 fabric. 



The observations made by Rosin (1946) on the tails of tadpoles 

 would support the latter possibility. Judging by the arrangement of 

 the pigment cells, which rest on a basal membrane of connective 

 tissue, it would seem that the intrinsic texture of this membrane must 

 consist of orthogonally trellised submicroscopic fibrillae of collagen. 

 As it cannot be split up into two lamellae, the two systems of fibrillae 

 apparently lie in the same plane. Rosin was able to show how the 

 orthogonal fibrillar system grows by "afline" enlargement of the 

 surface, the trellising of the two fibrillar systems always remaining 

 rectangular (Fig. 150). Intussusception is responsible for surface 

 enlargement, inasmuch as new submicroscopic fibrils are embedded 

 in parallel. 



