INTRODUCTION. ix 
their meeting in September, 1894; while in the 9th Edition of the London Catalogue of Brit- 
ish Plants published in 1595, these rules as respects the names of genera are largely followed; 
out of 440 genera in common with ours, all but 18 bear the same names as here given.* 
It cannot be too often repeated that the object of these rules is not to introduce new 
names, but to restore the old and the true ones. The rules of the botanists of the American 
Association, adopted as above, are as follows. A brief explanation of the objects attained 
by them is appended: 
RULE I. Priority of publication is to be regarded as the fundamental principle of botani- 
cal nomenclature. 
This has been generally acknowledged in theory as the guiding principle for determining 
which name should be borne by an animal or plant differently named by different writers. 
Various causes have retarded its application in practice. Its adoption is the only practicable 
way of securing stability to the original names. It has also been generally considered that 
the author who first defines or describes an animal or plant is entitled to the distinction of 
having his own name permanently associated with the name assigned to it; and this is also 
necessary for reasons of accuracy, because in numerous instances different plants have been 
called by the same name. In most cases the synonyms given in this work, with the date of 
publication, indicate the original name and the reason for its restoration under this rule. 
RULE 2. The botanical nomenclature of both genera and species is to begin with the pub- 
lication of the first edition of Linnaeus’ ‘‘ Species Plantarum ”’ in 1753. 
Some past date must of necessity be taken, in order to fix the limits within which prior- 
ity shall be reckoned. Prior to the publication of ‘‘Species Plantarum ’’ in 1753, the ab- 
sence of any general binomial nomenclature, and the meagre, uncertain and inadequate de- 
scriptions by most prior authors, make any earlier date beset with difficulties. The result of 
much discussion has been to fix that work, with which modern nomenclature substantially 
begins, as the ‘‘ point of departure.’’ That date received the endorsement of the International 
Botanical Congress at Genoa in 1892, and has since been accepted by most botanists in Amer- 
ica and Europe. Under this rule, no reference is made to names used prior to that work. 
RULE 3. In the transfer of a species to a genus other than the one under which it was 
first published, the original specific name is to be retained. 
From different views of the limits of genera, or from further knowledge of a plant, it 
often happens that it must be transferred to a different genus from that to which it was first 
assigned. Upon such a transfer, Rule 3 requires the original name of the species to be con- 
tinued, and preserves its stability. Thus, out of the genus Polypodium of Linnaeus, three 
other groups have been since carved, viz., Dryopleris ( Aspidium), Cystopteris and Phegop- 
teris. The Long Beech Fern (p. 19), called Polypodium Phegopterts by Linnaeus, belongs 
to the generic group named Phegopleris by Fée in 1850. Rule 3 forbids the use of the new 
specific name, fo/ypodioides, given to this plant by Fée, and requires the former specific name 
of Linnaeus to be preserved, and the plant thus becomes Phegoptleris Phegopteris, an acci- 
dental re-duplication that occurs in but few instances in the whole field of nomenclature. 
The Twin-leaf was called Podophyllum diphyllum by Linnaeus in 1753, and /effersonia binata 
by Barton in 1793; Persoon in 1805 restored the Linnaean specific name, making the plant 
JSeffersonia diphylla, the correct binomial under the rule, and the one which the plant has 
borne for nearly one hundred years. 
RULE 4. The original name is to be maintained, whether published as species, subspecies 
or variety. 
Plants and animals are continually described as species which subsequent authors con- 
clude are but varieties, and those first understood as varieties prove by subsequent study to 
be entitled to specific rank. Rule 4 maintains the first designation as the proper one, and 
avoids much confusion. Examples are numerous: See Figs. 28, 38, 61 ef seq. 
RULE 5. The publication of a generic name or a binomial invalidates the use of the same 
name for any subsequently published genus or species, respectively. 
Thus in the case of the Long Beech Fern, above cited, though the specific name po/ypod?- 
oldes is held to have been improperly given to it by Fée, the binomial, Phegopteris polypodi- 
oides, cannot be applied to any different plant; for if the earlier name should for any reason 
be lost or discarded, the name fo/ypodioides must remain available as the next lawful substi- 
tute, and thus the principle of nomenclature—once a synonym always a synonym. 
This rule operates to maintain one name only for a genus or species, and that, the first 
one applied to it, unless this was properly the name of another, in which case the next oldest 
* For a fuller discussion of this subject see articles by Professor Lester F. Ward, in ‘‘ Bulletin 
of the Torrey Botanical Club,’’ 22: 308-329, from which the above summary is mostly taken; by 
Professor C. E. Bessey, in ‘‘American Naturalist,’’ 29: 666-668; by Professor W. A. Kellerman, in 
“Journal of the Columbus Horticultural Society,’’ 10: 7-10, and in ‘‘ Botanical Gazette,’’ 20: 468-470; 
by Professor Conway MacMillan, in ‘‘Metaspermae of the Minnesota Valley,’’ 17; by Dr. B. L. 
Robinson, in ‘‘ Botanical Gazette,’’ 20: 97-103, 261-263; by Mr. F. V. Coville, in ‘‘ Botanical Gazette,”’ 
20: 162-167, 320-322, 428, 429; by Dr. F. H. Knowlton, in ‘‘ Botanical Gazette, 21: 82-85. 
