ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 59 



state of Australia. He notes two prevalent wheat-infecting rusts— 

 Puccinia graminis, or black rust which occasionally does very serious 

 damage, though the general dry weather which precedes harvest lessens 

 the danger of serious mischief ; and another common rust, P. triticina, 

 which only attacks the leaves of the wheat and is not of much economic 

 importance. 



Among smuts Urocystis Tritici is one of the most important. Infec- 

 tion of the host-plant occurs at the seedling stage before the wheat 

 appears above ground ; infected plants rarely produce grain. 



Ophiobolus graminis or " take-all," a pyrenomycetous fungus, also 

 gives serious trouble in wheat-fields. The seedling roots are attacked 

 and the fungus spreads upwards through the plant tissues. Barley is 

 also severely attacked ; oats less frequently. 



Fruit-trees suffer from Exoascus deformans, and from various shot- 

 hole fungi. These may spread from the leaves to the fruit and cause a 

 disfigured stunted appearance from the scabbed areas of the fungus 

 growth. 



Potatoes are the only root-crop of importance, and since 1909 

 PhytopMhora infestans has been recorded. Owing, however, to the dry 

 condition, it rarely causes the rot of haulms and leaves so common in 

 Britain. Sclerotia of Rhizoctonia are common, but though tubers are 

 frequently injured, the cause of injury is more probably Oospora scabies, 

 which does so much harm in the United States. Growers are hampered 

 by the small area of ground suitable for potato cultivation, so that it is 

 difficult to change the crop. 



& 



Lichens. 



(By A. Lobeain Smith, P.L.S.) 



British Wandering Lichen.* — Robert Paulson and Somerville 

 Hastings describe the origin and development of an unattached lichen 

 from the Downs near Seaford, but confined to a small area of about eight 

 acres. The specimens correspond to Parmelia revoluta var. concentrica 

 Cromb. At first it was suggested that the lichen may have commenced 

 life on some tree and been blown on to the downs. There were no tret- 

 bearing lichens anywhere near, and the problem was at last solved by the 

 discovery of some flints with Parmelia revoluta growing on them and 

 gradually becoming panniform. The lichens in time become dislodged 

 from the flints. They are very dry and are probably occasionally rolled 

 over by a strong wind. Some of them attain an almost spherical contour, 

 being made up of concentric layers of lacinia3. They are easily broken, 

 by the trampling of sheep, etc., and each broken portion may develop 

 anew. Erratic lichens occur elsewhere, but this is the only British lichen 

 with this peculiar habit of growth. 



* Knowledge, xxxvii. (1914) pp. 319-23 (9 figs.). 



