MELAMPSORA 353 
by looking in spring on fallen leaves of P. tremula, P. alba, at places where 
Mercurialis is found to be affected. The ceeoma on the latter is very 
capricious in its occurrence ; in some years it may be found almost every- 
where, in other years hardly a specimen can be met with. The large 
yellow spots show conspicuously on the upper surface of the leaves, so 
that when it does occur it is impossible to overlook it. 
There are two places near Birmingham where all the spore-forms occur 
year after year in close proximity: it is from these specimens that the 
descriptions are taken. In one case the teleutospores are on P. alba, in 
the other on P. tremula. 
The morphological differences of the four (or five) species of Melam- 
psora which appear on P. ulba and P. tremula are very slight. It is better 
to include them all for the present under Melampsora tremulae, as 
biological races. The fourth species is J/. Magnusiana Wagner, which 
has its ceomata on Chelidonium, and which, according to Klebahn, is 
identical with WM. Alebahni Bubdk, on Corydalis ; this has not yet been 
recorded for Britain, but Plowright mentions (Jc. p. 241) a Melampsora 
on P. tremula from which he could not obtain ceomata on either Larix or 
Pinus or Mercurialis—this might be M. Magnusiana. 
12. Melampsora Euphorbie Cast. 
Uredo Helioscopiue Pers. Disp. Meth. p. 13. 
Leeythea Euphorbiae Lév. ; Cooke, Micr. Fung. p. 221. 
Melampsora Euphorbiae Cast. Obs. ii..18, with plate (1843). Cooke, 
Handb. p. 523; Micr. Fung. p. 219, pl. 9, f. 193, 194. 
M. Helioscopiae Wint. Pilze, p. 240 (1884). Plowr. Ured. p. 236. 
Sace, Syll. vii. 586. Fischer, Ured. Schweiz, p. 508, f. 318, 
[Spermogones. Flat, hemispherical. 
Aicidiospores. Cxomata minute, }—} mm. diam. on the 
leaves, 1—4 mm. long on the stems, yellowish-red; spores in 
Fig. 264. M. Euphorbiae. a, teleutospores on E, exigua; b, teleutospore, 
and c, uredospore and paraphysis, on EL. Peplus. 
GU. 23 
