APPENDIX A. xi 



been opened or disturbed for about six months. When 

 accidentally observed a short time ago, it was found to exhibit 

 a flake-like cloudy mass near the surface of the fluid, which 

 I at first supposed to be some insoluble modification of 

 silica. On taking a portion of it out, and submitting it to 

 examination by a high power of the microscope, it was 

 observed that the cloudy mass was wholly composed of the 

 densely interlaced filaments of a fungus mycelium, some of 

 the branches seeming to originate from a large brownish- 

 yellow sporangium, which gave issue to multitudes of filaments 

 on all sides, whilst others bore tufts of spores. Concerning 

 the mode of origin of this fungus nothing can be said 

 it may, of course, have originated from a spore which had 

 gained access to the solution. The conditions of its nutrition 

 and growth do, however, present features of considerable 

 interest. It was growing quite close to the surface, and may 

 therefore have obtained its nitrogen either from the air or 

 from that dissolved in the surface-layers of the fluid. Did it, 

 however, contain carbon (from some impurity in the form of 

 a carbonate), or was this replaced in the structure of the 

 fungus by silicon from the silicate ? This is a question 

 which cannot at present be answered. At all events, the 

 fungus thrived in this solution, and seemed to grow much as 

 it would have done in a solution of ammonic tartrate 1 . 



In an experiment in which about ten minims of the weak 

 solution of iron pernitrate and seven of sodic silicate solution 

 were added to an ounce of distilled water, the fluid was boiled 

 for fifteen minutes, and the neck of the flask was then her- 

 metically sealed during ebullition. Some semi-gelatinous, 

 reddish-yellow flakes were deposited during the ebullition. 

 The vacuum being still well preserved, the flask was opened 



1 This observation naturally recalls those made by Messrs. Roberts 

 and Slack concerning the growth of fungi on freshly-prepared colloidal 

 silica. (' Quarterly Journ. of Microsc. Science,' 1868, pp. 105-108.) 



