142 



NATURE 



[August 3, ign 



It is not possible to give anything like an adequati 

 account of the numerous investigations which are 

 brought under review. After a brief discussion of 

 the metallic elements which are of importance to thi 

 algae, the non-metallic elements and compounds are 

 considered. Reference is made to the evolution of 

 oxygen in carbon dioxide assimilation and the various 

 methods by which it can be quantitatively determined. 

 Engelmann's well-known bacterial method and 

 Beyerinck's method of using luminous bacteria are 

 spoken of by the author as " two of the most elegant 

 methods for tile demonstration of the evolution of 

 oxygen." Beyerinck found that luminous bacteria, 

 when placed in contact with algal filaments, are phos- 

 phorescent when oxygen is being evolved, but cease 

 to be luminous in its absence. 



In reference to Bokorny's observations on Spirogyra 

 and Zygnema in support of Baeyer's hypothesis that 

 formaldehyde is the first product of carbon dioxide 

 assimilation, the author concludes that, in view of 

 their far-reaching scientific importance, it is neces- 

 sary that these investigations should be repeated with 

 absolutely pure cultures of algae. This appears to be 

 so much the more desirable as Treboux, working with 

 pure cultures of some of the lower algae, was unable 

 to obtain starch formation either with formaldehyde 

 or methylal. Dr. Riehter very properly lavs stress 

 upon the great importance of pure cultures in 

 these experiments in order to prevent the contamina- 

 tion with carbon dioxide produced bv fungal or bac- 

 terial growths, which may completelv vitiate the 

 results. He fully discusses the results obtained by 

 various observers upon the assimilation of organic 

 nutrient substances, such as glycerine. Many 

 alga: seem to prefer organic compounds containing 

 nitrogen ; others prefer carbohydrates. Among the 

 former are diatoms, and indeed these organisms 

 seem to have a preference for albuminoid food 

 substances. 



The second part of the book is taken up with a 

 consideration of the papers dealing with the poisonous 

 action of various chemical compounds, the influence of 

 narcotics, the deleterious effects of different spei ies 

 of algae upon one another, and the reactions of the 

 nutrient material upon their growth and development. 

 The poisonous action of minute traces of metals, 

 termed lv Naegell ( h , id\ nanii; is illustrated bj 

 some interesting experiments made bv the author to 

 show the deleterious influence exerted by coins when 

 placed in contact with diatom cultures on agar. In 

 discussing tin effects of light and temperature on the 



algae, the author shows clearly that variation in in- 

 tensity lias a verj marked effect on their growth and 

 on the formation of various organs. 



The book may he commended to students as .1 very 

 useful summary of the important researches bearing 

 upon algal nutrition and trie-various factors bv which 



it is controlled. Verj tew of the problems, of course. 



are peculiar to algae (they are problems of plant 

 nutrition generally), ami the Look is to some extent 

 lacking in completeness, because, in his desire to 

 confine himself strictly to algae, the author has 

 neglected man} papers dealing with plant nutrition, 

 NO. 2179, VOL. 87] 



which are just as applicable to algae as to other 

 plants. 



["here is a very full index, both of subjects and of 

 authors, together with a good table of contents and 

 a list of nearly live hundred references. 



H. VV. 



POPULAR ASTRONOM1 . 

 ( it Star-Lore for Teachers: Suggestions for the Teach- 

 ing of Astronomy by direct Observation, Experi- 

 ment, and Deduction. By B. Lowerison. Pp. 67; 

 interleaved for notes. (London : The Clarion Press, 

 n.d.) Price is, 

 (2) The Star Pocket-book; or. How to Find Your Way 

 at Night by tin- Stars. .1 Sample Manual for the 

 Use of Soldiers, Travellers, and other Landsmen. 

 By R. Weatherhead. With a foreword by Sir 

 Robert Ball. Pp. 80. (London : Longmans, 

 Green, and Co., 191 1.) Price is. net. 

 (;,) I.es Progres Reccnts dc V Astronomic (III. — annic 

 1909.) By Prof. Paul Stroobant. Pp. 174. (Brus- 

 sels : Hayez, Rue de Louvain, [911.) 

 (1) TF the automatic response to the stimulus of the 

 J- s'tarry heavens has not forced a man to acquire 

 enough astronomical knowledge to instruct his pupils 

 intelligently in star-lore, that man has no business 

 to be a teacher of the subject. Lacking the capacity 

 or desire to observe and find out for themselves, we 

 fear that such misplaced persons will gain little from 

 this book. 



The information is tabloidal, sometimes urn 

 awkwardly abbreviated, and the compilation bears 

 internal evidence of the lack of that fuller knowledge 

 so essential in anyone who professes to direct the 

 teacher. 



The motive is worthy, and as the book was written 

 " for love " we should, perhaps, modify the criticisms 

 that suggest themselves at once. But gamma is not 

 tin brightest star in Corona (p. eq). nor is Sirius a 

 notable Algol variable, as might be deduced from 

 p. 49; and objection may be taken to "astrology" as 

 a translation of " L'Astronomie." 



The children under the author's tuition probably 

 enjoy their astronomy lessons immensely, and he is 

 to be congratulated upon the modest but effective 

 equipment so thoughtfully provided for them. We 

 would that other teachers could be induced thus to 

 recognise the wonderfully educative potentialities of 

 astronomy, but we fear that, despite the excellent 

 intention, this small book can do but little to further 

 the recognition, 



(2) As a practical naval instructor, Mr. Weatherhead 

 was asked t" lecture to a number of army officers on 

 the use of the stars as guides in night marches, and he 

 now gives the general public the benefit of his admir- 

 able notes. A brief introduction, directions .is to how 

 to identify the chief stars, and a key to the nomen- 

 clature of them, are followed by some excellently 

 clear 1 harts showing the brightest, most conspicuous 

 groups. A few tables and examples make it clear 

 how to find north or south by three of the simplest 

 methods. All interested in the stars apart from their 



