96 



SCIENCE 



[N. S. Vol. XLVII. No. 1204 



Metagymnosperitiffi consisting of the Conifers 

 and Guetales. It is well point out that 

 Ginkgo forms a link between the two main 

 divisions. The long chapter on Coniferales 

 is chiefly devoted to an exposition of the 

 author's well-known view of the primitive po- 

 sition of the Abietinese, and especially of 

 Pinus, and the derivation of the ancient 

 Araucarinese from that group. This hypothe- 

 sis is maintained with great ingenuity, in 

 the face of much inherent improbability. The 

 opposite view of the direct derivation of the 

 Araucarineffi from their immediate Palseozoic 

 predecessors, the Cordaitese, has been consider- 

 ably strengthened by the work of Boyd Thom- 

 son and Burlingame. 



The view, maintained by Wieland and his 

 followers, of an affinity between the Bennet- 

 titales and the Angiosperms, is rejected. In 

 this connection it may be pointed out that 

 we have no actual proof that fertilization in 

 Bennettites was by spermatozoids, as the 

 author assiimes. 



The chapter on Herbaceous Dicotyledons 

 is important, for it sets forth in detail the 

 author's theory of their derivation from 

 arboreal ancestors, a view which is well worthy 

 of consideration. The author believes that 

 the fresh and vigorous herbaceous vegetation 

 will tend in future to supplant the forest 

 trees; he has no such hopes, however, for the 

 Monocotyledons, which he acutely remarks 

 (p. 198), may be said to represent the second 

 childhood of the vascular plants. " This 

 group seems to have reached such a high 

 degree of specialization that it will probably 

 in the long run entirely disappear and be re- 

 placed by new derivatives of the still plastic 

 dicotyledons" (p. 416). Such a consumma- 

 tion, however, is not likely to be reached while 

 man remains dominant. 



In the chapter on anatomical structure and 

 climatic evolution, the question of annual 

 rings is considered. While the author finds 

 no such rings in Cordaitean wood from Prince 

 Edward Island (Lat. 46° 30') he believes that 

 they are present in contemporary wood from 

 Lancashire (Lat. about 53° 30'). The differ- 

 ence of latitude seems too small to be signi- 



ficant, and most appearances of annual rings 

 in Carboniferous woods from any source are 

 fallacious. 



Chapter XXXI. is on a special subject, the 

 evolutionary principles exhibited by the Com- 

 positse, and is chiefly concerned with the some- 

 what narrow question of the distribution of 

 oil-canals. 



The concluding chapter is on anatomical 

 technique, including the sectioning of coal 

 and photomicrographic methods. On all these 

 subjects the author is an acknowledged expert, 

 and his counsels will be of the greatest value 

 to practical workers. 



The index might perhaps have been made 

 fuller with advantage. No references are 

 given in the book; the accumulation of refer- 

 ences often becomes a burden, but a few 

 would have been of service to the reader as 

 a guide to his future studies. 



In the present notice, attention has often 

 been directed to points which seem open to 

 criticism, or on which there is much difference 

 of opinion. These divergences of view in no 

 way detract from a high estimate of the 

 great interest and complete originality of 

 Professor Jeffrey's remarkable work. 



The illustrations, as one wotdd expect in 

 a book by this author, are abundant and ex- 

 cellent. 



D. H. S. 



SPECIAL ARTICLES 



ON THE SERIES IN THE ULTRA-VIOLET FLUO- 

 RESCENCE OF SODIUM VAPOR 



In two papers^ published by Professor J. C. 

 McLennan an account of the extension of Pro- 

 fessor "Wood's iodine vapor spectrum into the 

 ultra-violet is put forth. Professor McLennan 

 has not only proved that the resonance spec- 

 trum can not be obtained in the violet, but has 

 also proved " that we have to do here with a 

 case of ordinary fluorescence where Stokes's 

 law is followed and where fluorescence is stim- 

 ulated by the light from any one of a number 

 of wave-lengths of a limited portion of the 

 spectrum." In this ease the fluorescence spec- 

 trum begins at A.4600 and extends to A.2100, 



1 J. C. McLennan, Proc. Boy. Soc, LXXXVIII., 

 p. 289; XCL., p. 23. 



