With very quick growers, such as aluminic chloride, one 

 can see a very thin colourless, almost invisible, membrane 

 apparently streaming out from the top of the shoots while 

 one watches, looking like a plant cell or sometimes like a 

 small Medusa. This gradually seems to thicken and become 

 opaque. Similar observations may be made by forming a 

 little cell with parafin wax on a microscope slide, intro- 

 ducing a little silicate solution, adding a small crystal, and 

 covering with thin glass, then observing with a pocket 

 lens or low power microscope. I tried this method in order 

 to see if possible whether there were any indications of 

 crystals hring produced, but could see none, either during 

 growth or after growth appeared to have ceased. There 

 were no outlines of crystals, but when dried the structure 

 appeared to be of the nature of rounded nodules. It appears 

 almost certain that the precipitate forming the growth is 

 a silicate of the base, but one in which the basic oxide is 

 only loosely associated with the silica, since hydrochloric 

 acid dissolves out the base and leaves the silica, which 

 usually retains the shape it first assumed, although in some 

 cases it appears to sink down into a gelatinous looking mass. 



A careful analysis of the growth would be interesting, 

 but it is not easy to get a pure specimen, on the one hand 

 free from the unaltered salt, and on the other from the 

 silicate of soda. I have made one or two rough determin- 

 ations of the silica contents of the firmer growths, such as 

 ferrous and cupric salts. I poured off the silicate solution, 

 after growing a small crystal, washed the growth that 

 remained with water, dried and then estimated the anhy- 

 drous silica in the usual way. I obtained approximately 

 50 per cent, anhydrous silica, but I hope to make more 

 detailed and accurate determinations. 



Whatever may be the agency producing growths, it 

 appears that the shoots must be tubular, the solution of 



