Explanations of the Catalogue. 
M OKE than seventeen years have elapsed since the publication of the Tenth 
Edition of the London Catalogue. Many new species have been added to 
our native flora and the advance in critical botany has again made great 
progress. This is the more satisfactory as field-work during the period under 
review was partially interrupted through the dislocation brought about by the 
great war. 
Questions of nomenclature continue to be gradually settled on well-known 
principles which are now generally accepted. The aim of those who are 
responsible for the compilation of this new edition has been to make it as generally 
useful and helpful as possible as well as accurate and where long established 
names have again had to be changed a clue has been given, where thought 
necessary, by adding the old and better known name in brackets. To have done 
this in all cases would have made the catalogue cumbersome and thus have 
detracted from its usefulness in other respects. 
On this vexed question I cannot do better than quote the following remarks 
from one of Mr. Salmon’s recent letters : 
“It has seemed impossible to adopt a system of nomenclature that will 
satisfy all recent writers upon this difficult branch of botany and some- perhaps 
many — of the names used will be certain to find disfavour in some minds. When 
any species has had written upon it, apparently with good reason, many arguments 
both for and against its more modern name and conclusive evidence seemed 
wanting, what appears to be unstable has been rejected and a name has been 
adopted by which it can be recognised unmistakably by users of the Catalogue." 
The preparation of the Eleventh Edition of the London Catalogue has been 
rendered possible by the willing and unstinted labour of Mr. C. E. Salmon. It is 
he who has carried through a laborious piece of work which has made a serious 
inroad on his time during several years. He, too, with my approval and ready 
assent, secured the services of many of our leading experts in connection with the 
genera to which they have devoted special study. 1 am also grateful to Mr. Arthur 
Bennett for again supplying the comital numbers following each species. In 
keeping his copy of Topographical Botany posted up to date Mr. Bennett has 
rendered a great service to British Botany and especially to the compilers of the 
four last editions of the London Catalogue. 
Among those who gave great help in the preparation of the Tenth Edition of 
the Catalogue the following have passed to their rest :—The Rev. E. S. Marshall 
who with Mr, W. A. Clarke assumed the chief responsibility in its compilation, 
the Rev. W. Moyle Rogers who supplied the Rubus list in the Tenth Edition, James 
Britten who gave valuable advice on nomenclature, Henry Groves, the Rev. 
Augustin Ley and others to whom 1 expressed my gratitude in the preface of the 
last edition. 
Among those who have given similar valuable help on the present occasion are : 
Mr. W. H. Pearsall the Batrachian section of Ranunculus ; Mrs. Eliza S. 
Gregory the first part and Mr. E. Drabble the second part of the genus Viola ; 
Colonel A. H. Wollev-Dod Rosa ; Mr. C. E. Britton Centanrea ; the Rev. (. Roffey 
Hieraciutn; Mr. A. B. Jackson Thymus, Ulrnus and Poptdus \ Mr. E. G. Baker 
Plantago; Mr. J. Fraser Sali.v : Messrs. T. & T. A. Stephenson Orchidaceiv ; Mr. 
Arthur Bennett Potamogeton, Carex and Calamagrostis ; Mr. James Groves and 
Canon G. R. Bullock-Webster Charophyta. 
Their names are given in the order in which the genera for which they have 
so kindly undertaken responsibility occur in the Catalogue and a new feature has 
been introduced by inserting the name of an expert immediately following a 
generic name so that users of the Catalogue can see at a glance who is responsible 
for the arrangement of a particular group. To all of these experts I tender 
Mr. Salmon’s and my own grateful thanks. 
The notes which accompanied several of these lists are here appended, but an 
enormous amount of critical work throughout the Catalogue has been undertaken 
by Mr. Salmon himself to most of which no special attention is drawn. It may 
here be mentioned that the multitudinous forms of CapscUa and Taraxacum have 
been intentionally omitted, as it was feared the Catalogue would have become too 
unwieldy. 
