STRUCTURE OF GELS 



71 



TABLE IX 

 DISPERSION SERIES 



The entanglement of lianas in a virgin forest is a macroscopic net- 

 work system (Fig. 5 5). A good example of fibre network is the veil 

 of aerial roots of Cissus lianas in a tropical forest : thin filiform roots 

 with a length of several metres hang slackly from the branches. They 

 form, as it were, a fabric in the air, although none of these aerial roots 

 have grown together. In moving air this entanglement of roots be- 

 haves like a coherent mass because neighbouring filaments impede 

 free movement. There are many other, still finer macroscopic net- 

 work systems viz., skeletons of vascular bundles of leaves, succulent 

 sprouts and fruits (Fig. 56), skeletons of sponges (especially not- 

 iceable in silica sponges), spongy parts of bones, etc. An excellent 

 example of a meshwork with microscopic elements is macerated skin 

 (Fig. 57); also latex tube systems of the latex plants. When algae 

 threads are fished out of a pool, we are astonished to find how they 

 cling together in a tangled skein, although every thread is an individual 

 in itself. Here the junction bonds, which are hypothetic in the case of 

 gels, can actually be observed under the microscope, for at all points 

 where two threads cross, they stick together (cf. Fig. 51b, p. 66). The 

 number of these junctions is so great that a wad of algae like this is 

 even slightly elastic when compressed. 



We penetrate into the submicroscopic domain by making the 

 threads so thin as to become invisible under the ordinary microscope, 

 thus obtaining gels. Until recently their structural principles had to be 

 found out by indirect means (Frey-Wyssling, 1938). Nowadays, 



