106 Roberts & Slack, on Fang old Growths in Silica. 



matter further, employing different solutions of hydrate of 

 silica. Mr. Roberts found that all the air-dried specimens 

 of silica in the laboratory at the Mint contained bundles of 

 radiating fibres varying in diameter from 0*2 mm. to 0'5 mm., 

 and in some cases 1 mm. ; and when magnified the fibres re- 

 solved themselves into beaded cells. Specimens of the jelly 

 dried in vacuo were quite free from these fibres. Gelatinous 

 silica, stored in completely filled bottles, exhibited no fibres, 

 but they 'did occur in some other bottles which were only 

 partially filled. 



An examination of about fifteen specimens showed that in 

 no case was there any appearance of the passage of colloid 

 silica into crystalline silica. 



Mr. Barff, F.C.S., assistant to Professor Williamson, was 

 kind enough to prepare for Mr. Slack a solution containing 

 about 4 per cent, of silica, obtained by dialysis in University 

 College laboratory. In one specimen, which had been exposed 

 for a few days to the air, Mr. Barff" noticed threads, which 

 proved to be fungoid. He also found that similar threads 

 were not destroyed by contact with strong (cold) hydrochloric 

 acid, nor even by a mixture of hydrochloric and hydrofluoric 

 acids. 



All the specimens of silica solution supplied by Mr. Barff" 

 to Mr. Slack, whether kept in bottles nearly full and corked, 

 in bottles containing much air, or in open vessels, exhibited 

 the mildew threads in the course of a week or ten days. 



In order to test the aptitude of a solvit! on of pure dialysed 

 hydrate of silica to further the growth of fungoid vegetation, 

 Mr. Slack made the following experiments, selecting silica 

 solutions in which no trace of vegetation could be discovered. 



On the 26th March a small tube bottle Avas nearly filled 

 with the silica solution, a piece of mouldy cheese was placed 

 at the bottom, and the bottle corked. In a second bottle, 

 filled with the solution, a small piece of live moss was placed. 

 The next day the part of the solution immediately over the 

 cheese in the first bottle turned milky, and flocculent-looking 

 projections rose from the cheese. On the third day the solu- 

 tion was completely gelatinized and milky. 



On the 2Tth March a small portion of periosteum from a 

 mouldy bone was placed in a similar bottle and solution. 

 Gelatinization took place as when the cheese was employed. 

 No gelatinization occurred at that time in the bottle contain- 

 ing the moss. 



On the 31st patches of mould appeared at the top of tlie 

 first bottle, and the next day a similar growth was observed 

 at the top of the solution in the third bottle. 



