CERTAIN BRITISH HETERCECISMAL UREDINES. 
157 
spores not being mixed with paraphyses. This is P. phrag- 
mitis, Schum = (P. arundinacea, D. C.). The other, P. 
M a gnu si an a, Korn, has its teleutospores with much shorter 
pedicels, and they often form long black lines running down 
the sheaths and stems of the affected plant. Its uredospores, 
moreover, are deep orange in colour, and always, as far as I 
know, mixed with paraphyses. This species has in this country 
hitherto generally been regarded as a variety of Puccini a 
graminis, Pers. 
In a previous paper 1 I have shown that P. phragmitis has 
its secidiospores upon Kumex conglomeratus, crispus, 
obtusifolius, hy drolapathum, and Rheum officinale 
(Expts. 140, 178, 179, 180, 181, 182, 183, 334), and conversely 
that the secidiospores of iEc. rumicis thus produced, when 
placed upon Phragmitis, gave rise to the brown Uredo of 
P. phragmitis without paraphyses (148, 166, 172, 188, 189, 
208, 209). This being the case, it occurred to me, after 
reading Cornu’s 2 communication that it was just possible he 
might have confounded these two Puccinise, and that P. Mag- 
nusiana might have its iEcidium upon Ranunculus repens. 
This possibility was to me the more probable, because I had 
in 1882 fallen into a similar error, and I had then operated in 
the same manner as M. Cornu appears to have done, namely, 
by placing leaves and stems of the Phragmites upon the plant 
to be infected. Since 1882 all my cultures with these Puccinise 
have been made by germinating the teleutospores in a watch- 
glass, having previously separated them from the reed, and 
examining them microscopically to insure against error from 
the commingling of the spores of the two species. Now, it 
happened that after reading M. Cornu’s paper I found, in the 
autumn of 1883, a long, straight ditch full of reeds upon 
which at both ends, for about twenty yards, the Phragmites 
were completely blackened by P. Magnusiana. This ditch 
was about a quarter of a mile in length, and the reeds which 
1 Plowright, “ On the Life-History of the Dock -dEcidium,” ‘ Proc. Royal 
Soc.,’ No. 228, 1883, pp. 47 — 49. 
2 Cornu, ‘ Comptes Rendus,’ 26 June, 1882. 
