INTRODUCTION Xxill 
primitive, to be followed by the Gymnocarpex, with the three 
subseries in order of development :—1. Coniocarpinee ; 2. Gra- 
phidiner; 3. Cyclocarpines. In Cyclocarpine the more simple 
lecideine families should precede the great lecanorine group, 
which includes the most highly evolved lichens. 
The term “Order” has been retained in place of the now 
generally accepted term ‘‘ Family” to maintain conformity with 
Part II. The Orders that should have been included in the 
latter work are printed in the Appendix to the present volume. 
The sequence of arrangement adopted will be found at pp. 1-2, 
25-6 and 387-8. 
In preparing the Monograph it has been found necessary to 
depart in many instances from the scheme of classification and 
method of description adhered to by the Rev. J. M. Crombie in 
1894, but I desire to record my very great indebtedness to the 
work done by him both in his publications and in the herbarium 
of the British Museum. I wish to thank those who have 
generously sent me rare or new specimens:—Mr. Hebden, 
Rev. W. Johnson (especially for Sarcopyrenia gibba), Miss 
Knowles, Mr. Paulson, Mr. Travis, Mr. Watson and Mr. Wheldon. 
IT have also to thank Dr. Rendle for his ready advice, my 
colleagues in the Cryptogamic herbarium, Mr. A. Gepp and 
Mr. J. Ramsbottom, for their unfailing assistance in all 
doubtful points, and Mr. P. Highley for his careful drawings. 
The metric system has been used for measurement; the 
reek letter » indicates the one-thousandth part of a millimeter. 
Other abbreviations refer to chemical reagents: + signifies a 
colour-reaction, f + a faint reaction, — no reaction. Iodine solu- 
tion—(I), iodine | grain, potassium iodide 3 grains, water } oz., 
is used as a test for starch or glycogen ; potassium hydrate (K),— 
equal parts of caustic potash and water ; calcium hypochlorite 
or bleaching-powder (CaCl),—1 part in half its weight of water ; 
and nitric acid (NO.), indicate by colour-reactions the presence 
of lichen-acids in the thallus. K + yellow indicates a general 
yellow reaction; K*¥"ev, a reaction in the upper portion or 
cortex. K followed by CaCl frequently gives a reaction and is 
expressed thus :—K(CaCl) + yellow. The meaning of these 
varying reactions is that the colour of the acids is liberated by 
the application of an alkali alone, by bleaching-powder alone or 
after previous treatment with an alkali. Reactions cannot 
always be relied on, as the production of acids may have been 
inhibited by absence of light, etc. 
I. c 
