ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 329 



Fungi that Live on Paper.* — Pierre See has for some time given 

 attention to the moiilds that are found on damp paper. These are 

 generally Hyphomycetes and leave a coloured stain on the paper. The 

 spiores have presumably been entangled with the substances of which the 

 paper is made, and develop in suitable moist conditions. See has 

 cultured these fungi on carrot, potato, gelatin, bread, etc. He finds 

 that the same fungi recur frequently, and that the " paper fungus flora is 

 a comparatively limited one." 



Effect of Fungicides on Hop Mildew. f—E. S. Salmon has been 

 experimenting on the effect of sulphur solutions on Sphserotheca 

 Humuli. He does not agree with the opinion that the lethal agent is 

 the sulphur deposited from the solutions used. It is the solution that 

 kills the fungus. The fungus was easier to damage when in the conidial 

 stage, possibly because the walls of the hyphte are then thinner ; they 

 were also less resistant on an old hop-leaf than on a young one. If the 

 fungus is to be killed at the early stages, a stronger solution of the 

 fungicide is necessary. 



Plant Diseases. — J. Smolak | has made a contribution towards our 

 knowledge of silver-leaf disease in comparing the cytology of diseased and 

 healthy leaves. In silvered leaves the mesophyll is thicker ; the cells 

 of the spongy parenchyma are stimulated to growth in length, and the 

 intercellular spaces are more extensive. The nuclei of the cells tend to 

 become irregular or amoeboid, and are gradually disorganized ; evidence 

 was also forthcoming of amitotic divisions. The author concludes that 

 the diseased tissue resembles parasitized tissue, somewhat of the nature 

 of gall tissue, and suggests that the changes are due to the secretion of 

 a toxin by the leaves themselves. Bacteria were occasionally found in 

 the tissues. 



F. L. Stevens § records a disease of corn in Porto Eico due to an attack 

 of PhyllacJiora graminis. The fungus forms black spots on the leaves 

 and leaf-sheaths, each one representing a stroma in which are produced 

 the peritheoia of the fungus. 



F. D. Fromme and H. E. Thomas |1 have reported a destructive root- 

 rot of apple-trees prevalent in the orchards of Virginia, due, apparently, 

 to the conidial stage of a species of Xylaria. Two or more species of 

 Xylaria are involved, and more study is required. Apparently all varieties 

 of apples are susceptible, and probably equally so. 



L. Petri 1 gives additional notes on the chestnut disease. He finds 



* Comptes Rendus, clxiv. (1917) pp. 230-2. 

 t Ann. Appl. Biol., iii. (1917) pp. 93-6 (1 pi.). 



X Ann. Appl. Biol., ii. (1915) pp. 138-57. See also Bot. Centralbl., cxxxii. 

 (1916) p. 269. 



§ Phytopathology, vii. (1917) pp. 55-6 (1 fig.). 



II Phytopathology, vii. (1917) p. 77. 



•f Atti Reale Accad. Lincei, cccxiii. (1916) pp. 499-501. 



June 20th, 1917 z 



