196 SUMMARY OF CURRENT RESEARCHES RELATING TO 



recognize and combat fungal and other pests. He devotes the first 

 part of the book to a general discussion of plant life as regards the host, 

 and an account of the parasites by which they are liable to be attacked. 

 He then describes the life-history of various fungi, with a general 

 classification of the group, always confining his attention to such forms 

 as may be met with in the tropics. 



In the second part of the book he takes the host-plants in order and 

 then describes the diseases to which each is subject. Fungi are mainly 

 the exciting causes, though some attention is also given to other agents 

 such as insects, worms, physiological conditions, etc. The final chapters 

 are devoted to an account of the best method of prevention and cure, to 

 fungicides, spraying apparatus, etc. A bibliography and index are 

 provided. The book is well illustrated. 



Fungi occurring in Potato Plants.* — A large number of fungi 

 have been described associated as diseases or otherwise with the potato. 

 F. Krause has reviewed the literature concerned with these organisms 

 to determine which of them are originators of disease and which of 

 them are saprophytes. He finds that fungal hyphas are present in the 

 tissues of sound as well as of diseased plants, as has been likewise deter- 

 mined in various wild plants, Borago officinalis, Solarium Dulcamara, etc. 

 He does not think that the presence of fungi in leaf-roll disease proves 

 that these fungi are the cause of it, as the fungi appear only late in 

 the year, whereas the leaf-roll occurs during the summer. The fungi 

 present he considers to be only weak or " room " parasites. 



Krause gives a list of the fungi obtained by artificial culture from 

 such diseased potato plants, but he was unable by infection with the 

 fungi to reintroduce the disease. 



Snap-beech Disease.f — E. M. Prior has investigated a disease of 

 beech-trees, first noticed at Great Missenden, and later found to be 

 prevalent in the beech woods at Tring. The trunks of affected trees 

 snap off at a more or less constant height of 15 to 20 feet from the 

 ground at a diseased area, the base and the upper parts of the trunk 

 being sound. 



Investigation showed that the fungus Polyporus adustus was present 

 on the diseased part of the tree, and infection experiments by means of 

 mycelium placed on the bared sapwood of the living beech-stem gave 

 positive results and confirmed the view that the trouble was due solely 

 to the fungus. 



The writer is of opinion that the fungus enters through a wound, 

 and that the mycelium then spreads rapidly in a longitudinal direction, 

 but more slowly in a transverse direction. The cortex and bark are 

 reduced to a powdery white mass, and the woody elements destroyed in 

 time. The hyphae enter the cells by means of the pits, and the cell- 

 walls are attacked from the inside. The lignified membrane is reduced 



* Mitt. k. Willi. Inst. Landw. Brornberg, v. 2 (1912) pp. 143-70. See also Bot. 

 Centralbl., cxxv. (1914) pp. 112-14. 



t Joum. Econ. Biol., viii. (1913) pp. 229-63 (2 pis.). 



