[August, 1012. 



style of the book is a credit to the 

 publishers, and one can only regret that 

 they did not have the translation re- 

 vised by an Englishman ; as it stands, it 

 might serve a double purpose by afford- 

 ing correction exercises in English 

 grammar and composition for rural 

 schools. 



In Plant Pathology, 

 as in other subjects, the day of the en- 

 cyclopaedia has passed. Prof. Eriksson's 

 book deals only with the diseases of field 

 crops in temperate climates, and is 

 therefore the more valuable, since these 

 can receive fuller individual treatment 

 than is possible in a work which pro- 

 fesses to include all known diseases. But 

 this limitation renders impossible any 

 recommendations of the book to the 

 readers of the Tropical Agriculturist 

 (in spite of the translator's numerous 

 references to "planters" since, except 

 possibly for the section on club root, 

 they would find in it nothing of interest, 

 or at least of practical use, to them. 

 The following 



EXTRACTS FROM THE AUTHOR'S PREFACE 



gives the views of this experienced 

 plant pathologist on a subject which is 

 often debated by planters :— 

 ' ' Nowadays we frequently hear the com- 

 " plaint that the diseases of our culti- 

 " vated plants become year by year more 

 " numerous and more disastrous. It is 

 "alleged that new diseases are con- 

 " stantly turning up which have never 

 "before been seen or heard of. It is 

 " also said that parasitic fungi, which 

 '• hitherto have proved quite harmless, 

 " have changed their nature, and be- 

 " come most destructive. 



" Is this really the case, or is it not ? 

 " Some hold this opinion to be erroneous, 

 " and claim that the state is the same as 

 " before, but that greater attention and 

 "the strict investigation which now 

 "are given to this study bring the. 

 "matter more before the public eye, 

 " and also result in the discoveries of 

 " hitherto unnoticed diseases. 



" This explanation can hardly be gain- 

 " said. In most civilised countries there 

 " is now a diligent survey and a close 

 " inspection of the health of cultivated 



" plants, and this attention must result 

 " in a detection of diseases that have 

 "been previously unnoticed. But, on 

 " the other hand, there are many cases 

 " that cannot be placed summarily in 

 " this category. And this refers especi- 

 " ally to a great number of the 



"fungoid diseases. 

 " It is, after all, an incontestable fact 

 " that fresh fungoid diseases have re- 

 " cently appeared and are gaining a 

 " footing in various countries. How is 

 " this to be explained ? Several causes 

 " work simultaneously to this end. 



" The inclination in our time for spec- 

 ialisation, even with regard to agri- 

 " culture, inasmuch as only one or a few 

 " species are cultivated in large masses, 

 " helps to make the plants more suscep- 

 tible. This mass-culture of varieties 

 " and sorts generates new characteristics 

 " in the individual plants, and some of 

 " these new forms will then be more 

 "suscpetible to diseases and become a 

 " source of disease for the whole plant- 

 ation. 



" But another important fact must be 

 " placed 3ide by side with this. 



" THE LAW OF EVOLUTION 



"is known and accepted as truth in 

 "the scientific world. Formerly it 

 " was thought that hundreds and even 

 "thousands of years were required for 

 " this evolution. But to-day we are cer- 

 " tain that new forms can be brought 

 "forth through impulsive new form- 

 " ation — • mutation '—and these forms 

 " can vary from the parent stock in one 

 " or more characteristics. Why could 

 " not this natural law be applied also to 

 " the extensive dominion of the parasitic 

 "fungi ? And why could not these new 

 "forms of fungi possess qualities that 

 " would enable them to avail themselves 

 "of the nourishment offered through 

 " the new races of hostplants brought 

 "about by the mass-cultivation? This 

 " is quite possible, and recent experi- 

 " ments and observations tend to prove 

 " this supposition. 



"Beside these two purely scientific 

 "explanations, we have the practical 



