234 TltANSACTIONS AND PROCEEDINGS OF THE [Sess. LXVT. 



It is important to follow exactly the instructions, and 

 to use only pure ingredients, and special care must be 

 taken to prevent the sodium hydrate becoming moist by 

 contact with the fingers or undue exposure to the air. 



Into a ferfecUy dry and stoppered bottle of at least 

 200 c.c, put first the sodium hydrate. Add next the 

 xylol, and shake two or three times, and then add the 

 toluidin blue. Again shake briskly. At this stage the 

 liquid will appear blue, but the dye is merely in suspension ; 

 but, on adding the alcohol and shaking for a few minutes, 

 the colour will change to claret. The liquid should be 

 shaken occasionally during the next twenty-four hours, 

 and then filtered ready for use. In most cases it will 

 be found better to dilute it again with three times its 

 bulk of xylol, as the stain is too dark. The use of a more 

 dilute solution is referred to in Mr. Robertson's paper. 



It is not advisable to make a large amount of the stain 

 at one time, as, by exposure to light, precipitation occurs, 

 and the liquid becomes colourless. 



J. MUSGROVE, M,D., F.R.C.S. 



The Origin of the British Flora. By J. G. Good- 

 child, of the Geological Survey, F.G.S., F.Z.S., Custodian 

 of the Collections of Scottish Geology and Mineralogy in 

 the Edinburgh Museum of Science and Art. 



(Read 8th May 1902.) 



There are very few botanists of the modern school who 

 have not devoted some thought to the origin of the 

 particular fiora to which their attention happens to have 

 been turned ; and in thinking over some of the anomalies 

 in plant-distribution, they can hardly have failed to make 

 more or less inquiry into the ancestral history of the plants 

 in question. If we are to get a satisfactory answer to any 

 such inquiries, it has long been recognised that it can only 

 be obtained by searching Nature's Records of the Past. 

 These plainly enough inform us that the existing species 

 of plants have descended from a line of ancestors who have 

 survived through a long series of geographical, climatal. 



