792 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of i lie rust Puccinia malvacearum, of which the principal host is Althea 

 rosea, and after that Malva sylvestris. It has been found also on a large 

 scries of malvaceous plants. Eriksson considers that the disease is Bpread 

 liy means of diseased seeds, or by seedlings grown upon such seeds. He 

 refers the disease to the existence, in the first place, of a mycoplasm in 

 t he seed, and he describes the process of growth from the plasma condition 

 to the mycelium. He describes also the further infection of other plants. 

 P. Dietel * publishes the results of infection experiments with three 

 Uredineae, of which the Cseoma generation is found on Larix europsea, 

 and of which the spores all germinate at low temperatures. They differ 

 iy other respects very widely : in the time required from germination 

 until the production of the promycelium, and also in the influence 

 exerted on the spores by a long drying process. The species studied 

 were Melampsora Larici-caprearum, M. Tremulse, and Melampsoridium 

 Betulinum. 



Dissemination of Puccinia graminis.f — Experimental investigations 

 have been made by F. J. Pritchard to explain the dissemination of 

 Puccinia graminis. He gives an historical sketch of the subject, and 

 explains the methods adopted for the purpose of studying this question. 

 He then sums up as follows : — 1. P. graminis passed readily from wheat, 

 Agropyron tenerum, A. repens, Hordeum jubatum, andElgmus triticoitlr* 

 to the barberry. 2. Observed facts seem to oppose the theory that 

 ascidiospores and uredospores are carried considerable distances by wind. 

 3. Uredo pustules of Puccinia graminis appeared on winter wheat at the 

 same time as on grasses near the barberry bushes, and earlier (with one 

 exception) than on grasses remote from the barberry. 4. P. graminis 

 did not appear to spread to wheat by aid of the grasses. There are three 

 distinct biological forms. 5. Uredospores of P. graminis failed to sur- 

 vive the winter 1904-5 at Fargo, North Dakota. G. The wintering of 

 P. graminis as mycelium in plant tissues in North Dakota is very doubt- 

 ful. 7. The pericarp of rusted wheat is frequently filled with rust 

 mycelium and numerous pustules of teleutospores. 8. Teleutospores in 

 some of the germinating grains appeared to be germinating in a Palmella- 

 like stage. 9. Pieces of mycelium resembling rust were found in the 

 cells of the scutellum close to the growing plant. 



Sexuality of Uredineae.f — L. Kurssanow reviews this question in the 

 light of the work done on the subject by Blackman, Christman, and 

 Olive, and he then proceeds to give his own observations. The material 

 of Puccinia Peckiana Howe, with which he worked, was collected near 

 Moscow, and he describes carefully the sections cut through all the dif- 

 ferent stages of development, and gives the results of his research. He 

 finds in this species a conjugation of two entirely similar gametes. Olive 

 had described the conjugating cells in the species examined by him as 

 being always a large cell with a small one. Kurssanow thinks that the 

 difference of the species may account for the variations recorded, and he 

 also suggests that the passing over of the nucleus may be a pathological 



* Centralbl. Bakt., xxxi. (1911) pp. 95-106. 

 t Bot. Gaz., lii. (1911) pp. 169-92 (1 pi.). 

 X Zeitschr. Bot., ii. (1910) pp. 81-93 (1 pi.). 



