164 BOOKS AND CURRENT LITERATURE 



Pedagogically, the author makes a commendable digression from his 

 general treatment of the subject by introducing Mitscherlich's mathe- 

 matical expression of the law of minimum. Possibly few students for 

 whom the text was intended could decipher the expression; but the 

 introduction of the student, occasionally, to something he cannot quite 

 master is stimulating — A. E. Vinson. 



The Ferns of Oregon. — A very attractive popular account of the 

 ferns of Oregon has recently been issued^ from the herbarium of that 

 state. It is the joint work of Professor Sweetser, Miss Ruth M. Howell 

 and Niss Hannah M. Ken worthy. Thirty species of ferns are listed, 

 belonging to eighteen genera, but the fern-allies are not comprised in 

 the treatment. The key seems to be a very usable one, and is illus- 

 trated with pen and ink drawings. A brief statement is given of the 

 position of the fern group in the plant kingdom, and the mode of repro- 

 duction in ferns is described and illustrated. Although this descrip- 

 tion is designated non-sexual reproduction, it also includes an account 

 of sexual reproduction. There is a list of synonyms for such of the 

 ferns as are unfortunate enough to have more than one name. There 

 is also a bibliography and a glossary. The ferns of the north-west 

 are of such great interest that this work will be especially welcome as 

 an aid in gaining a knowledge of them. — -George B. Rigg. 



1 Sweetser, A. R. The Ferns of Oregon. Univ. Ore. Bull. N. S. 11, No. 2, 

 30 pp., 24 figs., September, 1913. 



