192 SUMMARY OF CURRENT RESEARCHES RELATING TO 



loj the quantity of starch-reserve contained in the cells of the leaf. In 

 silver fir a young- leaf with good insolation on a vigorous and healthy 

 branch can withstand infection. The fungus propagates itself on the 

 lower, slow-growing branches. In trees of defective grow^th the whole 

 crown may be attacked. 



A disease of sugar-cane in Hawaii, known by the native name 

 ■" iliau," has been investigated by Lyon * for the Sugar Planters' Associ- 

 ation. The fungus causing the disease is a pyrenomycete Gnomonia iliau 

 sp. n., the imperfect stage of which is a Melanconium. It attacks the 

 leaf -sheaths of the young shoots, entering; the tissues through the leaf- 

 bases below the surface of the soil. The leaf -sheaths by means of the 

 fungus are cemented into a rigid cone, which prevents the growth of the 

 stem-tip. 



The " wither- tip " of Citrus, a disease which manifests itself by 

 decayed spots on the leaves, has been studied by Roy E. Clausen. f It 

 was supposed to be due to a fungus CoJIetotrichum gJo^osporoides, but 

 careful experiments have shown that that fungus is only saprophytic, and 

 that the parasite is another form, which has been named Gloeosporium 

 Limefticolum sp. n. 



From infection experiments carried out by Howard S. Reed,J it has 

 been proved that the tomato blight is caused by Phytophthora infestans, 

 the potato disease. The tomato crop had suffered considerably from 

 disease in South-western Virginia. It has also been proved that the 

 fungus is carried over the winter and transmitted in the seeds, but it is 

 considered that the epidemics of tomato-blight have mainly resulted 

 from infection by diseased potato plants. 



E. I. Bartholomew § reports a rapid increase in recent years of the 

 apple rust, GymnosporangiumJuniperse-virginianse. The simplest method 

 of control is the destruction of the alternate host, Juniperus virginiana^ 

 but that is not always practicable. Spraying tests were undertaken, the 

 apple trees having been treated at the time the sporidia from the Ggmno- 

 sporangium spores would be likely to infect the apple — towards the end 

 of May. The results were entreraely satisfactory, and the disease was 

 brought well under control. 



Similar good results were obtained by N. J. Gildings and D. C. Neal || 

 in West Virginia, where the rust was doing serious damage. The spray- 

 ing materials used were Bordeaux mixture, commercial lime-sulphur 

 and atomic sulphur. All these materials were effective in controlling 

 the rust, provided the applications were made at the right time. 



P. J. Anderson and H. W. Anderson % describe two species of 

 Endotliia. One of these, E. virginiima sp. n., is a weak parasite and 

 grows commonly on dead bark and wood of Castanea dentata and 

 Quercus velutina ; the other, E. parasitica, is the origin of the chestnut 

 disease. 



"^ Exper. Stat. (Hawaii) Bull., ii. (1912) 32 pp. (1 pi. and 10 figs.). See also 

 Bot. Gaz.,Uv. (1912; p. 554. 



t Phytopath., ii. (1912) pp. 217-34 (2 pis. and figs.). 



X Phytopath., ii. (1912) pp. 250-2. § Phytopath., ii. (1912) 250-7. 



!1 Phytopath., ii. (1912) pp. 258-60 (2 pis.). 



f Phytopath., ii. (1912) pp. 261-2. 



