THE SKELETON OF THE PLANT 49 
considerable internal strain, the micelle attracting each 
other and tending to squeeze out the water. The latter, on 
the other hand, tends to separate the micelle. 
According to Strasburger, the molecules of the solid 
matter are held together by chemical affinity, and there is 
no definite aggregation of them into micell#. He pictures, 
therefore, a linkage of the atoms into a molecular network, 
the meshes of which are occupied by water. On either 
hypothesis the quantity of water is capable of considerable 
increase or diminution, and the wall can be made to swell 
up by causing it to imbibe more fluid. This can be brought 
about by exposing it to the action 
of strong mineral acids, such as 
sulphuric acid. The water is held, 
however, by the solid particles 
with very great tenacity. 
A different view of the composi- 
tion of the cell-wall was advanced 
some years ago by Wiesner. He 
held that the substance of the 
membrane as it ig first formed pig 49--Twoeenep Certs on 
consists of rows of granular bodies Woop, sHowina Srraririca- 
which he termed dermatosomes ; a Senerae 
these are ‘connected together by protoplasm which surrounds 
them. He based his view on the phenomena which accom- 
pany the disintegration of the wall by the action of strong 
alkalies. On this hypothesis the cell-wall is living while 
young and growing. The protoplasm exists in it between 
particles of solid matter, and it holds the water in its 
substance. 
The thickening which always supervenes to a greater 
or less extent upon the first formation of the cell-wall is 
brought about by the protoplasm in a way similar to the 
method of its original construction. Layers composed like 
the original one are continually secreted by the protoplast, 
and are deposited upon its exterior in apposition with the 
wall already there. Hence walls which have a perceptible. 
4 
