2 
EXPLANATIONS OF THE CATALOGUE. 
On Rubus the Rev. H. J. Riddelsdell writes : 
“This is revised pretty much along the lines laid down by Rogers since the 
publication of Edition Ten. The correction of census numbers has been conducted 
on principles of caution : it is better to wait for certainty than to have to retract. 
Some new varieties cited as of Rogers & Riddelsdell are Rogers’ work, published 
by Riddelsdell for this edition. Where a hybrid is listed, it concerns the name (of 
species or variety) next preceding. Thus under leucostachys, hybrids are listed 
before varieties not after them. The hybrid quoted under R. hirtifolius var. 
mollissiiniis (X corylifolim) is a cross into which that variety enters, not type 
hirtifolius." 
On Rosa Col. A. H. Wolley-Dod says : 
“ That the nomenclature is modified from that adopted in his Roses of Britain 
in that all forms are raised to the rank of varieties. This is done since the Catalogue 
does not recognise forms, so that many well-known names, if retained as such, 
would disappear from the list. The rank or status adopted in The British Roses is 
that which they should bear.” 
On Alcliemilla , Sorbus and Pyrus Mr. C. E. Salmon writes : 
“The Atchemilla vulgaris forms have been arranged in accordance with the 
numerous papers by Dr. R. Buser of Geneva and the genus Sorbus , which seems 
rightly separated from Pyrus , on the lines laid down by T. Hedlund in his 
Monograph (1901)." 
On Centaurca Mr. C. E. Britton writes : 
“ The list of Centaurea-forms follows the arrangement of species and varieties 
that appeared in papers in the Reports of the Botanical Society and Exchange Club 
for the years 1920 to 1922 inclusive, and entails a large increase to the number of 
names appearing in the Tenth Edition, London Catalogue. With the intensive 
study of highly-critical genera, an enlarged nomenclature is inevitable. It will be 
observed that the forms previously ranked as subspecies of C. Jacca are now given 
independent status. This is probably a correct estimate of these Jacea- allies, 
which seem clearly differentiated by the laciniated, more indurated, only slightly 
concave, and not bullate, closely-investing appendages. 
The census numbers, it is believed, do not adequately show the distribution of 
the various forms. The available records indicate C. obscura and C. nemoralis as 
generally spread throughout the British Isles, with the second-named predominant. 
The more recently segregated forms appear to especially character se southern 
England, and, in certain districts, elsewhere, seem absent. No good reasons have 
come to light to reverse the conclusions arrived at as to the undesirability of 
perpetuating such names as ‘ dccipiens’ etc., that appeared in former editions of 
this Catalogue." 
On Hieracium the Rev. J. Roffey writes : 
“ So much good work has been done in the past that we may now claim to be 
fairly well acquainted with .the forms of British Hieracia , though undoubtedly 
some still await recognition. The work before us in the future lies in the 
co-ordination of these forms with those of the Continent. Zahn’s recently com¬ 
pleted monograph has therefore been taken as the basis of the present list. This 
has involved considerable changes in arrangement and also a good many in 
nomenclature, together with some amount of uncertainty with regard to some of 
the coinital numbers. It should be clearly understood that the ‘species’ of the 
present list are not species in the ordinary sense of the word, but sub-species or 
micro-species. Zahn arranges his plants under capital or group-species, each of 
which has as a rule many sub-species attached. Pilosella Linn., for instance, has 
no less than 624. As the plan of the Catalogue does not admit of sub-species it has 
been felt better to drop the capital species and take the sub-species as species, 
rather than reduce them all to the rank of varieties. About forty of these capital 
species are represented in Britain." 
On Melampyrum G. Beauverd’s Monograph of the genus published in 1916 
has been followed. 
