1883.] 



On the Life History of the Dock JEcidium. 



47 



reason that I have sought to extend my observations to other 

 compounds of titanium, and to vary the nature of the reactions 

 involved in the chemical process. Unfortunately it is found that 

 comparatively few bodies containing titanium lend themselves to the 

 purpose of atomic weight determination. I am, however, making 

 observations with the tetrabromide, which, in some respects, is to be 

 preferred to the tetrachloride, and the results furnished by its analysis 

 will be given in a second communication, which will also contain 

 details respecting the preparation of the substances used, the methods 

 of weighing, the processes of manipulation, effect of errors, &c. 

 With reference to the tetrabromide, I may here say that I find it can 

 be very easily made by the action of hydrobromic acid gas upon the 

 chloride, and that this proves to be a more convenient method of 

 preparation than that by which it was first obtained by Dappa. 



III. " On the Life History of the Dock iEcidium (JEcidium 

 rumicis, Schlecth)." By Charles B. Plowriuht. Com- 

 municated by W. Thiselton Dyer, M.A., F.R.S. Received 

 November 10, 1883. 



This iEcidium, which is common in this country upon Bumex 

 hydrolapathum, Huds., obtusifolius, Linn., crispus, Linn., and con- 

 glomerate, Murray, was regarded by Fuckel* and Cookef as being 

 a condition of Uromyces rumicis (Schum.), is now stated by Winter^ 

 in his last work to be a condition of Puccinia magnusiana. Daring 

 the present year I have conducted a series of cultures, in which the 

 life history of this fungus has been carefully, if not laboriously, 

 worked out, from which it appears that JEcidium rumicis bears the 

 same relationship to Puccinia phragmitis (Schum.) ( = P. arimdinacea, 

 D.C.) as uEcidium berberidis, Gmel., bears to Puccinia graminis, Perss. 



History of the Subject. — Winter, in 1875, § showed that those 

 botanists who had associated this iEcidium with the Uromyces rumicis, 

 simply because these two fungi occurred upon the same host plant, 

 were wrong, and that the fungus in question was the secidiospore of 

 Puccinia phragmitis. Stahl, in 1876, repeated Winter's experiment, 

 .and confirmed it. Now it happens that there are two Puccinice 

 common upon Phragmitis communis, the P. phragmitis (Schum.), and 

 P. magnusiana, Korn.|| In March, 1877, Schroter^" placed the spores 



* Fuckel, " Symbol. Mycol.," p. 61 



f Cooke, " British Uromyces," Grevillea, VII, p. 136. 



X Winter, " Rabenhorst's Kryptogamen-Flora," 1881, p. 222. 



§ Winter, " Hedwigia," 1875, vol. xiv, pp. 113-115. 



!| Kornicke, " Hedwigia," 1876, vol. xv, p. 179. 



^[ Schrdter Cohn, " Beitrage zur Biologie der Pflanzen," vol. iii, Heft I, pp. 

 ^65-6(5. 



