﻿Charcoal imiyregnated luith Slag. 37 



— elm and oak. As in the first case, the rods exhibit in a 

 remarkably well defined manner all the structural features 

 of the vessels from which they were derived or within 

 which they were formed. 



In the facts thus obtained from a direct examination of 

 the material itself, we have conclusive evidence that 



1st. Siliceous matter, either in a molten or a soluble 

 condition, was taken into the vessels of oak and elm 

 wood, or into the charcoal derived therefrom, and even- 

 tually deposited there. 



2nd. That the volume of material was sufficient to 

 completely fill all the vessels in large pieces of coal or 

 wood, and thus to form complete casts of these structures. 



It thus becomes necessary to obtain answers to the fol- 

 lowing questions : — 



1st. Was the silica taken up by the living plants or by 

 the charcoal derived therefrom. 



2nd. In what form was the silica taken up ? 



3rd. In what way was entrance into the tissues of the 

 coal effected ? 



1st. The evidence of the specimens themselves shows 

 beyond question that the silica must have been taken up 

 before the structure of the tissues was destroyed by 

 combustion. It must, therefore, have been taken up by 

 the living plant or by the charcoal before the latter was 

 subjected to a destructive oxidation. 



With respect to the first of these alternatives, we 

 fortunately have important guiding data in the known 

 processes of silicification in plants. So far as we know, 

 silica can enter the living plant only through its roots in 

 the form of a soluble silicate. Its final disposition leads 

 not to the filling up of vessels, but to such a distribution 

 within the substance of the walls of tissues as to give to 

 these latter a marked element of mechanical strength. 

 Instances of this kind are familiar in highly silicified hairs 

 of the nettle and squash, as also in the very highly 



