THE AMERICAN BOTANIST 11.^ 



not thereafter return to the usual form. For a time it was 

 held that all advances in evolution were due to discontinuous 

 variation and the unlike forms which result from it, but the 

 studies of many investigators have shown that discontinuous 

 variation may produce small variations that are just as stable 

 as large ones. That many new species have originated by 

 n^utation can scarcely be doubted but that other species fully 

 as good have arisen through the small variations described 

 by Darwin is equally certain. Continuous variation, could of 

 course, originate nothing. It is only when such a variation 

 swings so far in one direction that it cannot return that new 

 species may result, but in such a case it is no longer a con- 

 tinuous variation. Any further variation must be around a 

 new set of characters; that is, around a new species or variety. 



BOOKS AND WRITERS 



A second edition of John N. Martin's "Botany for Agri- 

 cultural Students" being needed, the author has taken the op- 

 portunity to change its title to the more appropriate "Botany 

 with Agricultural Applications." At the same time various 

 errors in the text have been corrected, new matter has been 

 added, additional illustrations provided and other illustrations 

 improved. The book is now an octavo of more than 600 pages 

 and 488 illustrations. The subject matter of the book is that 

 of the usual textbook, but it differs from others in drawing its 

 illustrative material chiefly from agricultural sources. It is 

 issued by John Wiley & Sons, New York, and costs $3.50. 



* * * 



The author of a recent botanical work, published by him- 

 self, boasts in his advertising that he allows no discount to 

 dealers. Apparently he expects the seller of books to work 



