FUNGI WHICH CAUSE TLANT DISEASE 83 



2. If any justification were needed for adding to the growing 

 library of works on plant diseases, it would be found in the 

 economic importance of the subject. The cultivation of plants 

 involves the crowding together of species which entails the danger 

 of epidemic attack, so that some comparatively innocuous and 

 negligible fungus becomes by opportunity a destructive parasite. 

 Thus new attacks by fungi or by animals are constantly being 

 discovered, and the life-history of the organism causing the disease 

 must be traced before effective remedial measures can be applied. 



The books before us are both by American writers well-known 

 for their work on the diseases of plants, and though they are 

 more or less restricted in scope they are of interest and value to 

 all students. 



The volume by Dr. Stevens is, he tells us, " intended to intro- 

 duce to the student the more important cryptogamic parasites 

 affecting economic plants in the United States," but as fungi, and 

 especially those that cause diseases of plants, are largely cosmo- 

 politan, the book is fitted to be of world-wide service. It often 

 happens that some part of a plant already injured becomes covered 

 with fungal growths, and it is extremely important to know 

 whether such fungi are of parasitic or saprophytic habit. 



Dr. Stevens has gone over the whole field from Myxomycetes 

 to Fungi imperfecti, selecting those fungi that are known to have 

 caused trouble. He gives synoptic tables and diagnoses of 

 families and genera that are either proved or suspect as the 

 cause of disease, and lists the species that are fatal ; in the case 

 of American species he supplies full descriptions. The Fungi 

 impcrfecti are classified and described as such, but where the full 

 life-history of these forms has been worked out, references are 

 given to the perfect forms. The book is well illustrated, and is 

 provided with copious bibliographies, a glossary of the terms 

 employed in the text, and an index of hosts and parasites. It can 

 be recommended with confidence to all students of this very 

 extensive and difficult branch of botany. 



3. Dr. Cook deals only with the diseases of tropical plants. The 

 demand for the vegetable products of the tropics, such as cotton, 

 rubber, cocoa, &c., has increased enormously, and the book has 

 been written with a view to help the planters in their struggle 

 with new and adverse conditions. 



The first few chapters give in order a survey of plant life ; the 

 nature and symptoms of disease ; the structure and function of 

 plants ; the classification of fungi ; and an account of various 

 causes of plant disease. Other chapters are devoted to a short 

 account of slime-moulds, phanerogamic parasites, bacteria, insects, 

 worms, and, lastly, functional or physiological diseases. Most of 

 the diseases are due to fungi, and a discussion of these occupies 

 the larger part of the earlier chapters. 



The second and more extended part of the work deals with the 

 host-plants in due order and the maladies that attack them, 

 starting with corn and rice, and winding up with forest and 

 ornamental trees. Preventative and curative agencies are also 



