ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 517 



grows on the branches of various Phanerogams, Friinus, Fiper, etc. in 

 tropical countries. It is not parasitic on the brandies, but lives sym- 

 biotically with insects (Coccidi^O- Only the conidial stage is formed 

 and resembles somewhat Bornetina corlum, a vine fungus that occurs 

 associated with cochineal insects. 



G. Arnaud * has given an account of peach blister due to the fungus 

 Exoasctis deformans. The fungus attacks not only the leaves, but the 

 young branches and the fruits. It does serious harm by causing the 

 fall of the leaf and thus lessening the nourishment of the tree. Arnaud 

 has described the infection, and the developmental stages of the fungus, 

 and he gives advice as to the best way of checking the disease leased on 

 the knowledge of the life-history of the fungus. As inoculation takes 

 place on the formation of the buds, a vigorous application of Bordeaux 

 mixture is advised at that early stage. Later sprayings are to be applied 

 as the bud bursts because young leaves are infected by spores that have 

 persisted on the branches. It has not been found possible to re-infect 

 older leaves. 



Discussion of Silver-leaf Disease.! — F. T. Brooks records the 

 observations and experiments that have been made in recent years in 

 connexion with this disease by himself and by other field pathologists. 

 Silvering of foliage is a wide-spread phenomenon, and is, he considers, 

 probably caused by various means, chief among them being the para- 

 sitism of the fungus Stereum purpureum. The silvered appearance of 

 the leaves is due primarily to the presence of air either below the 

 epidermal cells or in the cavities of their walls. Brooks records instances 

 of silvering among fruit-trees, directly attributable to the attack of the 

 fungus. He has also observed silvering on plants of the white dead 

 nettle, in which no fungus had any part. 



Methods of inoculation and of treatment are given, and the author 

 then gives his own views as to the nature of the disease. He considers 

 it to be a general pathological phenomenon which may be caused in 

 several ways, only one of these, Stereum purpureum^ being certainly 

 kno\m. It may also arise owing to some physiological disturbance, 

 possibly some interference with the transpiration current. 



Lichens. 



(By A. LoRKAiN Smith, F.L.S.) 



Thallus of Calcareous Lichens. t — S. Bachmann has followed the 

 development of the alga as well as of the symbiotic tissue of a species 

 of Opegrapha within the substance of a limestone rock. He found 

 that the alga, a species of Ghroolepus, had itself pierced not only the 

 looser lime-granules, but a crystal of calcium. When associated with 

 the fungus It was more restricted to a gonidial zone, though solitary 



* Kev. Phytopath., i. (1913) pp. 24-7 (2 figs.). 



t Journ. Agric. Soc, v. (1913) pp. 289-308 (2 pis.). 



X Ber. Deutsch. Bot. Gesell., xxxi. (1913) pp. 3-12 (1 pi.). 1 



