60 BOTANICAL GAZETTE [JULY 
3. The ligulate Wolffias of the United States, by CHARLES HENRY THOMP- 
Son. Under this title reference is made to the subgenus Wolfiella, which 
the author is inclined to believe is a distinct genus intermediate between 
Wolfia proper and Lemna, but unfortunately it has never been known to pro- 
duce flowers. Only one form has been credited to the United States, and that a 
variety of the Mexican W. g/adiata, known only from the subtropical region 
of Florida. Mr. Thompson found it among the collections of Bush, made in 
the swampy region of southeastern Missouri, and has also discovered the 
Mexican W. dingudata in California, growing in an irrigation canal near 
Bakersfield. A careful account of these two forms is given, illustrated by 
three plates.—J. M. C. 
A popular work on ecology. 
UNDER the somewhat uncertain name of The Great World's Farm, a 
valuable and delightful work has been written by Selina Gaye.? The title 
was suggested by a passage in Professor Drummond’s account of untrodden 
Africa, and refers to the way in which plants establish themselves and 
flourish unattended by man. 
The subjects treated are the natural methods of soil formation, water and 
food elements in soil and air, the action of leaves and roots, flowers and their 
pollination, the distribution of seeds, friends and foes, the chances of life, 
changes due to man, and similar matters. 
This enumeration of subjects does not, however, give any suggestion of 
the great diversity of topics and the extraordinary array of facts which have 
been brought together. The work is written from the most modern point of 
view, and although dealing with scientific matters, technical terms have been 
so skilfully avoided, that any well informed person may read the book with 
enjoyment, without possessing previous knowledge of the subject, or of its 
terminology. The volume also contains much about worms, insects, birds 
and other animals in connection with the account of vegetation. There are 
so few lapses from full scientific accuracy that they may be ignored by both 
reviewer and reader. Some of the historical statements may be taken 
with a grain of incredulity, such as the story of the Persians keeping 
pollen of the date for nineteen years during a civil war in order to secure 4 
crop of fruit at its close, yet they are Currently accepted and serve to accent- 
uate general truths. : 
The book is well printed and the illustrations, mostly full page plates, 
are especially commendable. Altogether the work forms a compact volume 
of entertaining and instructive information, and can be heartily recommende 
to the lover of nature whether dilettante or earnest student.—J. C. A. 
*GaYE, SELINA.—The great world’s farm; some account of nature’s crops 
and how they are grown. With a preface by G. S. Boulger. 8vo. pp. x + 365: 
Illustrated. London: Seeley & Co. 1893. Chicago: The Macmillan Co. $1.59. 
