ON PRUNUS 209 
Teleutospores. Sori similar but blackish-brown; spores 
ellipsoid to oblong, composed of two globose cells which readily 
separate (or lower cell often narrower, paler and imperfect), not 
thickened above, densely and coarsely verrucose, brown, 30— 
45 x 18—25 »; pedicels hyaline, very short, deciduous, spring- 
ing in clusters of about 10—20 from a common base. 
kcidia on Anemone coronaria, A. nemorosa, April and May; 
uredo- and teleutospores on Prunus domestica, P. insititia, 
P. spinosa, also on cultivated species and varieties of Prunus 
_and its allies, August—October. Common in certain districts. 
(Figs. 155, 156.) 
The discovery of the hetercecism of this parasite is comparatively 
recent. Tranzschel first showed (in 1904) that it was hetercecious, using 
Anemone coronaria and Amygdalus communis as the alternate hosts. 
F. T. Brooks, at Cambridge in 1911, laid fresh eecidiospores from the same 
species of Anemone on both sides of certain leaves of a “ Victoria” Plum, 
leaving others uninoculated. The plant was enclosed by a bell-jar, 
and three weeks later twenty-three of the inoculated leaves were found to 
bear on their under-surface uredo-sori of P. Pruni-spinosae, while the 
control leaves showed no signs of the rust (New Phytologist, x. 207). 
Arthur, in the United States, proved a similar fact, but in that case the 
host of the alternate phase was Hepatica acutiloba, a very close ally 
of Anemone. The xcidium is also reported on other species of Hepatica, 
Anemone ranunculoides and other species of Anemone, Eranthis hiemalis, 
and various species of Thalictrum. 
Scribner (Report of the Dept. Agric. U.S.A. 1887) describes the Puccinia 
as found on Cherry, Apricot, and Peach: it is recorded by McAlpine 
on leaves, fruit and stems of Peach and Nectarine, and leaves and fruit of 
Almond and Apricot. 
Trichobasis Rhamni of Cooke (Seem. Journ. Bot. ii. 344, iv. 104) on 
“ Rhamnus catharticus,” which was afterwards referred by him to this species 
(Handb. p. 508), is probably an error due to a mistake in the identification 
of the host. He states that the Puccinia on the same leaf was absolutely 
identical with P. pruni-spinosae, and omits the reference in the fourth 
edition of “ Microscopic Fungi.” No one else has found such a Puccinia 
on Rhamnus. The leaf in “ Micr. Fung.” ed. i. 210, is no doubt a Prunus 
leaf. 
The mycelium of the ecidial stage is perennial ; it penetrates in spring 
into the growing shoots which become deformed, the affected leaves are 
narrower and paler, and the flowers are usually imperfect or altogether 
wanting. These plants it is which cause fresh infections of the Plum-trees 
G. U. 14 
