PREFACE 



Since this little volume was started more work has been done on 

 mycotrophy. Yet the status of the subject remains unchanged. It 

 is still considered by most botanists— who are the only people to whom 

 even the word is familiar — as a specialty which should be listed 

 under the general heading of pathology. Mostly it is not listed at all. 

 Mycorrhizae are still considered abnormal structures occurring chiefly 

 on pine roots; while by some curious aberration the mycotrophic 

 structures found in prothallia and in rhizomes are likewise termed 

 mycorrhizae. Fungus-roots are found in rootless plants! There is, 

 moreover, a common impulse to lump all symbiotic phenomena 

 together, as odds and ends and thrown together in a heap, so that 

 the mycotrophist (if such a term may be used) is expected to be 

 interested in cases of algae growing in higher plants, or of small 

 insects found living in plant tissues. It is hoped that this book, in 

 spite of its obvious faults, may serve to show how mycotrophy is 

 separated from other phenomena, and how widespread is the 

 mycotrophic habit. 



Europe continues to be the center of mycotrophic study. In spite 

 of war, a considerable number of papers has appeared in this part 

 of the world in the last few years. Only a few papers on the subject 

 have been published on the other continents. 



Tree mycorrhizae continue to attract attention. Bjorkman 

 (1944) has made important studies in Sweden. In Poland, Dominik 

 (1946) has published interesting papers on fruit-tree mycorrhizae 

 which were produced on all trees studied. Endotrophic mycorrhizae 

 which were stimulated by applications of farmyard manure to the 

 soil were found by Sabet (1946) on Citrus in Egypt, while Smith 

 (1944/45) in Queensland found that "decline" in mandarin was 

 associated with depletion of the soil and consequent interference with 

 mycorrhizal activity. These results lend support to the idea that 

 internal processes in at least certain trees can be controlled by appro- 

 priate manipulation of the habitat. 



