268 



SCIENCE. 



[N. S. Vol. XXII. No. 557 



to determine readily under which genera a 

 given specific name has been applied, precisely 

 at what place and, incidentally, by whom. The 

 nomenclatorial confusion resulting from the 

 widely differing schemes of classification 

 adopted by various writers has long since be- 

 come so pronounced as to offer a very serious 

 obstacle to constructive work. What the 

 ' Index Kewensis ' has meant to botanists in 

 general and Paris's ' Index Bryologicus ' 

 .atterly to students of mosses, those who have 

 dealt with ferns have realized only partially, 

 hitherto, in consulting Moore's ' Index Fili- 

 cum,' a work that was printed from A only 

 midway through G in the years 1857-1862. 

 It is true that Salamon's ' Nomenclator der 

 Gefasskryptogamen ' (1883) has been of assist- 

 ance, although citations are entirely omitted; 

 but, if we consider the activity of fern stu- 

 dents in the last two decades alone, it becomes 

 evident from the wide range of descriptions in 

 periodicals — botanical and otherwise — how 

 little security in the use of new specific names 

 has been justified, and some idea may be 

 gained of the difficulties that have lain in the 

 way of ready reference to original d,escriptions. 

 Christensen's ' Index ' is designed to meet this 

 condition. Judging from the cliaracter of the 

 two parts at hand we have little doubt that 

 opinion can not fail eventually to be substan- 

 tially and deservedly favorable. 



With regard to the mechanical execution of 

 the work little but praise may be said. The 

 typography is exceedingly well adapted to its 

 purpose; and the method of citation is practi- 

 cally in accord with the common American 

 usage, the sequence being: (1) name, (2) 

 author, (3) title of serial, (4) series, if any, 

 in Roman capitals, (5) volume number in bold- 

 faced Arabic, (6) page and (7) date. , In a 

 very few cases well-known works and periodi- 

 cals are abbreviated in an extreme fashion 

 which, for the sake of avoiding cumbrous repe- 

 tition seems quite justified. Accepted species 

 stand under their proper genera in heavy-faced 

 print ; very doubtful species and those known 

 only among gardeners in italics; synonyms in 

 ordinary brevier. The listing of subgenera 

 in distinctive typography is also to be strongly 

 commended ; for, although our latest American 



rules contain no provision that these must be 

 taken up in the event of segregation, yet the 

 desirability of their later use is scarcely open 

 to question, and it is of high imiDortance that 

 such as are needed be used in their proper 

 sense and that all be held available. 



There is evidence of great care in citation, 

 and of unusual effort to prevent a possible 

 misconception as to the authorship and publi- 

 cation of new names and ' new combinations,' 

 of which there are of necessity a good many. 

 In transferring a species from one genus to 

 another, the resulting binomial, if new, is dis- 

 tinctly indicated as such; not, however, in the 

 usual way, by the phrase ' comb, nov.' but by 

 ' C. Chr. Ind. [page] 1905 ' ; by which means 

 the binary name of every recognized species — 

 whether proposed formerly or in this volume — 

 is accompanied by citation of publication. 

 More than a few of Dr. Christ's species are 

 here first referred to other than their original 

 genera; but in most, if not all, of these cases 

 that author is credited with the new binomial 

 (the citation being printed ' Christ in C. Chr. 

 Ind. [page] 1905,'). in recognition of assistance 

 received in preparation of the manuscript. 



Criticism of the major systematic treatment 

 must be deferred until the appearance of the 

 final brochures, for not until then shall we 

 have a formal presentation of the classification 

 adopted, nor shall we know how widely this 

 treatment departs from that of its professed 

 model, Engier and Prantl. There is, however, 

 some indication of a more liberal acceptance of 

 genera. Still, we can not but regard Anaxetum 

 Schott as worthy to stand quite apart, generic- 

 ally distinct, from Polypodium; and recent 

 studies ^ have convinced us that a more valid 

 genus than Adenoderris J. Sm. is hardly to be 

 found in the whole range of the Dryopteridese. 

 In the recognition of species the policy of the 

 author has been to follow the disposition of 

 monographers; in this way, de Vries's numer- 

 ous species of Angiopteris are admitted, though 

 under protest, on the ground that there has ap- 

 peared no later revision. 



Aside from the preparation of a modern 

 ' Synopsis Filicum ' — an undertaking so diffi- 

 cult and comprehensive that, under present 



"- Botanical Gazette, 39: 366-369. May, 1905. 



