48 DB. LAUDER LI:N^DSAT ON CHEMICAL REACTION 



nients of 1850-53. The colour was nearly as fugitive as where 

 the bleaching- solution was added to an alcoholic solution of the 

 colorific principles. Sometimes scarcely a trace was left on the 

 lichen of the application of the reagent; sometimes a fulvous 

 stain was left, or it was orange-red, or exhibited various shades 

 of red or yellow ; occasionally there were differently coloured 

 stains on the same plant. Sometimes a beautiful orange-red was 

 permanent ; more generally the stains in question gradually faded. 

 Sometimes the soredia were affected when the general thalline 

 surface was not ; at other times the presence of soredia was im- 

 material in assisting or obstructing the exhibition of the reac- 

 tion. Sometimes the same branchlet showed in different parts 

 every shade of crimson, as well as no reaction at all. As a general 

 rule, the reaction was most vivid where the thallus was pale, thin, 

 and soft, — least so where it was dark, thick and coriaceous, corru- 

 gated and warted. Fertile specimens generally showed it less 

 vividly than sterile ones. These remarks apply generally to all 

 the species of the genus examined. 



i2. tinctoria frequently gave no reaction. This was almost in- 

 variably the case where the thallus was dark-coloured and coria- 

 ceous. Sometimes there was only a faint tinge on the soredia. 

 Even the smaller, paler, more delicate forms never exhibited the 

 reaction nearly so vividly as R. fuciformis. 



i2. pJi^cQpsis: reaction generally vivid where thallus pale- 

 coloured. 



S. fuciformis^ including its varieties Montagnei and others : 

 reaction sometimes vivid crimson in one part and very faint or 

 absent in another part of the same plant j faint or absent gene- 

 rally in the more central, coriaceous, and thicker portions of 

 thallus. 



None of the Boccellce gave me aay reaction with bleaching 

 solution of soda. 



Nylander says that the young thalli of jB. tinctoria and pTigcopsis 

 exhibit distinctly and beautifully the erythrinic reaction, the 

 older being very little coloured ; but he goes on to remark that (as 

 I understand him), whatever he their colour-reactions, these 



differ specifically ^ and cannot 



opsis 



guished from each other " (p. 3G0). In truth, I regard ^Ay 



as a mere passage form, or connecting link, between tinctoria and 



fuciformis 



fucifc 



reaction 



