ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 495 



Witches-brooms on Hickory Trees/' — F. C. Stewart describes these 

 brooms as consisting of compact clusters of short upright branches. 

 They measure up to two-thirds of a metre when bare, and are larger when 

 in foliage. The writer has found the fungus Microstroma Juglandis on 

 the leaves of the brooms, and he concludes that their presence is due to 

 that fungus. 



Fungi Toxic to Bees.f — Gote Turesson has been studying the cause 

 of bee paralysis, and has come to the conclusion that it is due to moulds. 

 These infest hives that are poorly constructed, and the bees wintering in 

 them are very liable to the disease. The author has. proved his 

 contention by culture methods, securing his fungi from the intestines of 

 dead bees and mixing the material with honey. The moulds used were 

 PenicilUum sp., F. stoloniferum, P. conditaneum, Mucor mucedo, and 

 Gladosporkim. herharum. There was an equal degree of toxicity in 

 PenicilUum sp., P. stoloniferum, and Gladosporiutn lierbanim ; PenicilUum 

 conditaneum was the most virulent, and next in degree Mucor mucedo. 



The harm to the bees is not caused by parasitism, but by the toxic 

 substances of the hyphse, phenol, or phenolic acids. The action is at 

 first stimulating, and later comes paralysis of the nerves and the death 

 of the bees. Bees fed with pure honey were used in control experiments 

 which confirmed the finding from the mould material. 



Diseases of Plants.^ — B. A. Rudolph describes disease spots on 

 cherry-leaves which he has diagnosed as due to Alternariu Citri var. 

 Gerasi. This is a wound parasite and may produce spots on various 

 plants. Many culture experiments were undertaken and are fully 

 described. 



H. T. Giissow § publishes some notes on the pathogenic action of 

 Rhizoctonia on potato. He notes the absence of fine rootlets in plants 

 that have been attacked, and considers that the destruction of these root- 

 lets is the main injurious action of the fungus. 



A report of the Horticultural Branch of the Board of Agriculture || 

 deals with the prevalence of various serious diseases. Gooseberry mildew 

 (American) has decHned, the favourable result being due to spraying 

 methods which have been perfected. Another method of counteracting 

 the disease is to tip the tender shoots which are affected ; lime-sulphur 

 and Bordeaux washes have also proved effective. Wart disease of 

 potatoes has spread, but energetic means are being taken to deal with 

 the trouble. Immune varieties of potato are strongly recommended, 

 and seed from infected soil should not be used, as the soil attached to 

 the healthy potato may carry the disease. Corky scab of potato 

 {Spongospora suhterranea) has also been frequently notified. It is found 

 that weather conditions, such as a wet season, greatly increase the disease. 



* Phytopathology, vii. (1917) pp. 185-7 (1 fig.). 

 + Svensk. Bot. Tidskr., xi. (1917), pp. 16-38. 

 X Phytopathology, vii. (1917) pp. 188-97 (3 figs.). 

 § Phytopathology, vii. (1917) pp. 209-13 (1 fig.). 

 I'l Journ. Board Agric, xxiv. (1917) pp. 146-52. 



