Ward. — Recent Researches on the Parasitism of Fungi. 45 
provisionally, he asks ‘ ob beide Pilze durch Aenderung der Wirthpflanzen 
in einander iiberfuhrbare Formen einer Species zu nennen sind oder zwei 
distincte, wenn auch sehr nahe verwandte Species.’ It is almost certain 
that De Bary would, in the light of our present knowledge, have agreed 
with Klebahn (98, p. 131) that they are ‘ mehr biologische als morpho- 
logische Arten.’ 
Caeoma Laricis is the aecidium-form of an Uredine on the Larch, the 
connexion of which with an uredo-form has only lately been demonstrated ; 
it is now known to be the aecidium of a Melampsora found on willows 
(98, p. 149). Klebahn’s investigations have shown that spores from 
some of the aecidia (Caeoma) on the Larch readily infect Salix 
viminalis , S. cinerea , S', aurita , &c. ; less readily S'. Caprea , S', fragilis , 
S', daphnoides , &c., S. acutifolia. Other spores from aecidia, quite 
indistinguishable morphologically, readily infect S', daphnoides , and 
especially S', acutifolia , but have so far obstinately refused to infect 
S', aurita or S’. Caprea ; while S. viminalis and S. cinerea seem to be 
immune or very nearly so. 
Klebahn concludes that we have here two Fungi on the Larch which, 
though biologically distinct, have not yet become sharply differentiated 
one from the other (98, p. 150). In other words, the Larch Caeoma is in 
process of splitting up into two as yet incipient species. 
Puccinia Pringsheimiana , Kleb., and P. Ribis nigrae-acutae , Kleb. 
(I am not concerned in defending the bad nomenclature), both grow on 
Carex acuta , L., and form their aecidia on species of Ribes : this aecidium 
was long known as Ae. Grossidariae. Klebahn (98, p. 150) found that 
although P. Pringsheimiana and P. Ribis nigrae-acutae are practically 
indistinguishable by any morphological characters, the former develops 
its aecidia with ease on the Gooseberry and some other species of 
Ribes, except on the Black Currant : occasionally the latter host may 
be very feebly infected, but out of all comparison with the virulent infection 
of the Gooseberry. P , Ribis nigrae-acutae , on the other hand, infects 
R. nigrum easily and virulently: it also infects some other species of Ribes, 
but on R. Grossularia the infection is poor and uncertain, and rarely 
proceeds further than the development of spermogonia. 
Here we have, according to Klebahn, a case similar to the last, but the 
separation has proceeded further, and the biologically incipient species are 
more differentiated. 
The Fungus previously known as Puccinia Bistortae , Strauss, may 
be cited as a third case. 
Infection experiments appear to show that at least two forms of 
Puccinia are comprised under this name on Polygonum Bistorta. One 
of these forms its aecidium-stage on Conopodium , as Soppitt showed 
(161, 1893, p. 4, and 162, 1895, P- 773)? and was the first instance known 
