310 THE JOURiVAL OF BOTAT^Y 



Les Maladies ijarantaires des Plantes : Infestation- Infect Ion. 

 By M. NicoLLE and J. Magrou. Pp. 199, 8 fr. net. Masson 

 & Cie, Paris. 



During recent years the belief that all infectious disease, what- 

 ever the parasite and whatever the host, is one huge problem, has 

 attracted many disciples. Possibly the experiences of war have 

 widened our outlook on disease in general as well as given us a 

 number of pictorial representations of what attack and defence really 

 mean, and how a state of comparative stability may arise : it may be 

 that the Western Front was a clearer picture of symbiosis than is the 

 more altruistic vision of the text-books. 



The problems of phytopathology differ essentially from those of 

 human pathology in that plant-cells have walls ; and related to this 

 is the absence of circulation. As a direct consequence, we have no 

 acquired immunity in plants, and there is no serum-therapy. In the 

 search for generalisations, however, medical men have begun to take 

 an interest in phytopathology. The book before us is a ^jre'c/s of 

 parasitic diseases of plants written by two members of the staff of 

 the Pasteur Institute. There are five sections, which deal respectively 

 with diseases caused by insects ; parasitic flowering-plants ; diseases 

 ciused by cryptogams ; bacterial diseases ; and general problems. 

 The book has been written from a medical standpoint, and the ter- 

 minology is that of medicine rather than of plant patholog}'" ; in this 

 way, many interesting analogies are suggested. A large number of 

 diseases are described, together with the mechanism of infection and 

 the lesions produced. The descriptions, however, seem far too brief 

 to give more than an impressionist idea of the subject ; and the 

 absence of figures, jettisoned in order to keep 'the price within the 

 means of students, robs the volume of most of its value for them. 

 If the subject were placed in an examination syllabus the book would 

 prove extremely useful for examination purposes with its numerous 

 headings and brief sentences. We imagine that medical men in this 

 country would prefer a book writ large. 



J. R. 



BOOK-NOTES, NEWS, etc. 



Ti[E Essex Naturalist for April-September contains an interest- 

 ing paper on the " Birch Groves of Epping Forest," the Presidential 

 Address delivered by Mr. P. Paulson at the annual meeting of the 

 Field Club last March. " Within the past fifty years there has been 

 a great increase in the number of birch trees ; where there were tens 

 there are now thousands. No detailed suggestions as to the probable 

 cause or causes for the remarkable increase " had been made until 

 Mr. Paulson took the matter in hand ; in the present paper he gives 

 a summary of the history of the birch in the Forest, where for the 

 last three centuries it was by no means common, and a detailed 

 account of his observations which he sums up as follows : — " The 

 factors that have tended to bring about the great birch invasion may 

 be summarized as : 1. Leaching of soil, a factor of primary importance ; 

 2. Extensive felling for many successive years ; 3. A long series of 

 fires, especially those of recent date ; 4. Browsing of large herds of 



