ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 223 



Spongospora subterranea.* — I. E. Melhus, J. Rosenbaum, and E. S. 

 Schultz have made an exhanstive study of the geographical extension of 

 this fungus in the United States, of the nature of the soils which become 

 infected by the disease, and also of the disease-galls and accompanying 

 fungi. It has been known in the States for some time, and is capable 

 of persisting in the soil for five years. The roots are generally attacked, 

 and the presence of the fungus gives rise to small white galls. The 

 canker of the tuber is more rare, as the growth of the potato is fairly 

 rapid. 



The histology of the galls which occur on other hosts than 

 Solanwn tuberosum bears considerable resemblance to the histology of 

 Plasmodiophora Brassicse. 



Several types of dry-rot follow Spongospora ; the most serious is 

 caused by Phoma tuherosa sp. n. Many other fungi accompany or 

 follow the disease, and traces of them abound in or on the tubers, notably 

 the bulbils of Papulospora coprophUa, which bear a great resemblance to 

 the spore-balls of Spongospora. 



Treatment of seed-tubers lessens the disease, as does treatment of 

 the soil with sulphur, but no radical cure has yet been discovered. 



Work has been done on this disease also by Gr. B. Ramsey.f He had 

 observed that the hot dry season of 1916 was unfavourable for the 

 development of the disease, so he undertook a series of parallel cultures 

 of potato-plants in soil known to be infected with Spongospora. The 

 pots containing the plants were grown in different conditions of tempera- 

 ture and moisture, and the results showed that a cool moist season or 

 climate is most favourable to the development of the disease. There was 

 no infection when the temperature was high or when the soil was too dry. 



Diseases of Plants. | — J. E,. Weir describes a new fungus, Hypo- 

 derma deformans, which causes a serious disease of the needles of 

 the Western yellow pine {Pinus ponderosa) in Idaho, Washington, 

 and Montana. It induces a conspicuous hypertrophy by the extension 

 of its mycelium into the tissues of the twigs, and also through the 

 destruction of the youngest needles, thereby impairing very seriously 

 the vitality of the trees. Another effect of the fungus is the formation 

 of spherical-shaped witches'-brooms on trees past the seedling stage. 

 The brooms may weigh 100 lb., and measure 5 or 6 feet in diameter. 



E. S. Schultz § has investigated the disease of Silver-scurf on potatoes, 

 caused by the black mould Spondylocladmm atrovirens. He found it to 

 be a slow-growing fungus, taking ten days for development in culture 

 media. The spores vary enormously in size, measuring from 18-64 /x 

 in length in the same culture. The fungus enters the tuber by the 

 lenticels or through the epidermal layers, and destroys the outer layers 

 of corky cells ; owing to the products of the coloured spores the whole 

 tuber may become sooty-black. Infection may take place at any time 

 throughout the storage season. 



* Journ. Agric. Research, vii. (1916) pp. 213-53 (9 pis. and 1 fig.). 

 t Phytopathology, viii. (1918) pp. 29-31. 



X Journ. Agric. Research, vi. (1916) pp. 277-88 (1 pi. and 4 figs.). 

 § Journ. Agric. Research, vi. (1916) pp. 339-50 (4 pis.). 



