OCTOBEB 28, 1910] 



SCIENCE 



601 



standards of the Milton Bradley Co., as con- 

 tained in this book of Professor MuUiken's, 

 it would be possible to accurately describe and 

 identify the exact shade of the characteristic 

 sample dyeings, without pasting a single 

 sample in the book. And, by a proper system 

 of classification, the chemist attempting to 

 identify a color, after determining its class, 

 and dyeing a sample, would determine its ex- 

 act place in the color table, and so avoid the 

 necessity of hunting it up in the sample books 

 of the different color houses, or in his own 

 sets of home-made samples. 



To be of real value, such a treatise should 

 be written by a well-trained color chemist, 

 thoroughly familiar with the dyestuffs of to- 

 day, from their practical side, and accus- 

 tomed to face, in his regular work, the many 

 and varied problems in textiles, paper-making, 

 pigments, food products and the like, which 

 appear every day in a large dyeing laboratory. 



The theoretical part of such a book could 

 be easily obtained from the treatises we have 

 at present, including this one of Professor 

 MuUiken's. But the use of the color stand- 

 ard would give opportunity for identifying the 

 shades with a minimum of trouble and ex- 

 pense; and if the writer would incorporate 

 some of the regular laboratory information 

 about methods, and about the practical peculi- 

 arities of the different dyestuffs, their ease of 

 dyeing, comparative fastness, special uses, 

 cost prices as compared to others of the same 

 or different classes, and a host of other minor 

 matters of practical interest to users and 

 workers with the dyestuffs, such a book would 

 be hailed with enthusiasm by dyeing chemists 

 from one end of the world to the other. 



Charles E. Pellew 



October 5, 1910 



SCIENTIFIC JOURNALS AND ARTICLES 



The contents of the American Journal of 

 Matliematics for October are: 



" (/-Difference Equations," by Rev. F. H. Jack- 

 son. 



" On the Relation between the Sum-formulas of 

 Holder and Cesaro," by Walter B. Ford. 



" Sur un Exemple de Fonction Analytique Par- 

 tout Continue," par D. Pompeiu. 



" Symmetric Binary Forms and Involutions," by 

 Arthur B. Coble. 



" Systems of Tautoohrones in a General Field 

 of Force," by Harry Wilfred Reddiok. 



" The General Transformation Theory of Differ- 

 ential Elements," by Edward Kasner. 



BOTANICAL NOTES 

 TWO RECENT BOOKS ON LICHENS 



Within a few weeks of each other two 

 notable contributions to our knowledge of the 

 lichens of this country have been issued. The 

 first is Albert W. C. T. Herre's "Lichens 

 Flora of the Santa Cruz Peninsula, Cali- 

 fornia," published in the Proceedings of the 

 Washington Academy of Sciences (Vol. XII., 

 No. 2) and bearing date of May 15, 1910; 

 while the second is Bruce Fink's " Lichens of 

 Minnesota " published in the Contributions 

 from the United States National Herbarium 

 (Vol. 14, Part 1) and bearing date of June 1, 

 1910. The first contains 243 pages, and the 

 second 256 pages, with 51 plates and 18 text- 

 figures. They are both nominally local lichen 

 floras, and judged by their titles alone might 

 be supposed to present a similar mode of 

 treatment. However a comparative examina- 

 tion of the two works shows a marked differ- 

 ence between them. Thus while both accept 

 Zahlbruckner's general understanding of the 

 lichens, the first author proceeds at once to 

 the descriptive part of his book, evidently as- 

 suming that the reader will bring to its 

 perusal all the necessary loiowledge for its 

 full understanding. In Professor Fink's 

 book, on the contrary, there is an explanatory 

 introduction in which there is a discussion of 

 the nature of lichens, and the views that have 

 prevailed during the past two centuries. This 

 is followed by a particular discussion of what 

 is known of their structure and reproduction, 

 including under the latter sexual reproduc- 

 tion. Here he says " the sexual processes 

 have not been studied in very many of the 

 fungi most closely related to the lichens, but 

 recent discoveries seem to indicate that sex- 

 uality is common there and in the ascomyce- 

 tous lichens as well. In Collema, Stahl and 

 others have found that the apotheeium is 



