326 SUMMARY OF CURREMT RESEARCHES RELATING TO 



solution of ammonium sulphide containing 0'18 p.c. of sulphur; it 

 leaves no deposit on the leaves or fruit, and is therefore not distiguring, 

 as lime or other washes are. Full instructions are given on the mixing 

 and using of various sprays. 



Study of Rhizoctonia violacea.*— J. Eriksson recalls his experi- 

 ments on the diseases of carrot, beetroot and rape, caused by RhizoctoniUy 

 and the conclusion at which he arrived that in all three instances the 

 fungus was the same species and was a sterile form of Hypochnua 

 violuceus, though on these plants it never reached the higher stage. 

 It was only on such plants as Sonchus arvensis, S. ohraceus, Myosotis 

 arrensis, Urtka dioica, etc., that the higher fruiting form was produced. 

 In the present paper Eriksson gives results of a series of cultures, more 

 especially with two forms E. medkaginis and R. Asparagi, the first 

 a viralent disease of lucerne. Specimens of lucerne were examined, 

 the roots of which were covered with a violet mycelium ; where the 

 mycelium was thick and abundant no fruiting stage was to be noted, 

 but where it was thin perithecia of Leptosphaeria circinans were found 

 in groups. Though spore cultures have not yet been completely 

 successful in reproducing the Rhizoctonia stage Eriksson has no doubt 

 that the two are connected, and that the fungus on lucerne is therefore 

 different from the one on carrot. 



The fungus on Asparogm was also tested ; in this case sclerotia 

 were freely formed on the outside of the roots, but as no spore-form was 

 found the systematic position of the fungus is undetermined. Attempts 

 to inoculate other plants with either of these Rhizoctonia species were 

 unsuccessful. • 



Diseases of Plants caused by Fungi.f — V. P. Stewart has written 

 an account of the leaf-blotch disease of horse-chestnut, which affects a 

 large percentage of the foliage on mature trees in the eastern United 

 States, and is particularly destructive in nursery plantings. Both leaves 

 and petioles are affected, and sometimes the miniature fruits ; the disease 

 is marked by the dark red blotches on the leaves. The writer discusses 

 the various fungi that have been described as causing the disease, 

 and determines the ascogenous stage to be Guignardi JEscuU nov, comb. 

 Pycnidia are the first fruiting form to appear, scattered on the upper 

 surface of the leaf. Later, spermogonia are formed, with minute oblong 

 spermatia, and along with these latter the perithecia. Full descriptions 

 are given of the developments of these different bodies. In the early 

 stage of ascus formation a uninucleate cell enlarges and gradually 

 assumes the shape of the mature ascus, which at length contains eight 

 ascospores. Xo intermediate stages were observed. Inoculation experi- 

 ments were successfully carried out, and artificial cultures were made, but 

 no fruiting-bodies were formed on these. Stewart recommends dusting 

 with sulphur, or spraying with Bordeaux mixture, soon after the foliage 

 is developed. 



J. G. Grossenbacher % has had under consideration the various diseases 

 of citrus-trees. There is a group of diseases affecting the bark known as 



* Ark. Bot., xiv. (1915) No. 12, 31 pp. (12 pis.). 



t Phytopathology, vi. (1916) pp. 5-19 (4 pis. and figs.). 



; Phytopathology, vi. (1916) pp. 29-50. 



