192 REPORT OF THE BOTANICAL DEPARTMENT OF THE 
Holland it is so abundant that in many localities the culture of 
white pines is impossible. It is also reported from Belgium,!® Den- 
mark,!” Norway,!® Switzerland,’® France,” Austria?4 and Eng- 
land; 
Judging from the European literature on the subject, it appears 
that as a currant disease Cronartium ribicola is regarded as of little 
importance even in those regions in which it is abundant, but as a 
disease of white pines it has caused much damage. 
American mycologists, believing that it must eventually make its 
appearance in this country, have been on the lookout for it for many 
years; but with the exception of the Bartholomew collection pre- 
viously mentioned (footnote 2, p. 189) it has not been found any- 
where in the Americas. No Cronartium on any species of Ribes 
and no Peridermium on Pinus strobus are known to America. The 
fact that America is the home of the white pine makes the absence 
of Cronartium ribicola especially noteworthy. Magnus, Klebahn,™ 
and others have commented upon this and discussed the probable 
origin of the fungus. The most plausible theory advanced regard- 
ing the origin of Cronartium ribicola is that its original host was the 
Swiss stone pine, Pinus cembra, and that it was introduced into 
Germany in recent times from Russia where Pinus cembra forms 
extensive forests. Schellenberg expressed the opinion that it is 
also indigenous in the Swiss Alps on Pinus cembra. 
It is altogether probable that the apparent absence of Cronartium 
ribicola from America is real; or at least the fungus cannot have 
existed here long. It is unlikely that collectors have overlooked it. 
Both on the currant and on the pine it is conspicuous and readily 
identified. The horn-like masses of teleutospores are characteristic 
and serve to distinguish it from other rusts occurring on Ribes 
leaves. 
* Nijpels (44); Marchal (41), (42). 
7 Rostrup (53). 
* Blytt (7); Schoyen (56). 
* Fischer (15); Schellenberg (55). 
” Poirault (51). 
*v. Wettstein (67); Bubak (8). 
* Plowright (48), (49), (50). 
* Magnus (36), (37), (30), (40). 
“Klebahn (25), (26), (30, p. 155), (34, p. 78). 
* Schellenberg (55). 
