REED: SPECIALIZATION OF PARASITIC FUNGI 369 
and also uredospores produced by aecidiosporic inoculations were 
also used. As the result of the experiments, Jacob concludes that the 
rusts on Polygonum amphibium and on P. convolvulus and P. dume- 
torum are distinct. The relationship of these two forms may be 
indicated as follows: 
1. Puccinia Polygoni-amphibit Pers.; aecidial stage on Geranium 
albanum, G. columbinum, G. dissectum, G. lucidum, G. molle, 
G. nodosum, G. pratense, G. pusillum, G. pyrenaicum, G. rivulare, 
G. rotundifolium and G. sanguineum; uredo and teleuto stages 
on Polygonum amphibium. 
2. Puccinia Polygont Alb. et Schw. (P. Polygoni-Convolvuli DC.); 
aecidial stage on Geranium columbinum, G. dissectum, G. molle, 
G. pusillum, and G. rotundifolium; uredo and teleuto stages on 
Polygonum convolvulus and P. dumetorum. 
It may be noted that the same species of Geranium occur as hosts 
for both races, although the host list for Puccinia Polygoni-amphibii 
includes more species than the other. 
Puccinia absinthii DC. Klebahn (91) suggests the probability of 
specialized races in this rust although no cultural experiments have 
been carried out. He reports, however, minute differences in the spore 
measurements of the different forms. The following races are indicated: 
1. Absinthit on Artemisia absinthium. 
2. Artemisiae on Artemisia vulgaris. 
3. Abrotani on Artemisia abrotanum. : 
Puccinia bullata (Pers.) Winter. This rust, according to Semadeni 
(135, 136), has a race specialized to Silaus pratensis and one to Thys- 
selinum palustre. 
Puccinia carduorum Jacky. Probst (112) recognizes three special- 
ized races in this rust. 
I. Crispi on Carduus crispus and C. personata. 
2. Deflorati on Carduus defloratus. 
3. A third race probably occurs on Carduus nutans. 
Puccinia Centaurea Mart. Jacky (64) and Hasler (62) have both 
studied the specialization of this rust. Jacky suggested the occurrence 
of two specialized races: (a) Jaceae on Centaurea Jacea and (b) Ner- 
vosae on C. nervosa. Hasler separates out three rusts, making them 
species and finds additional host specialization in one of these. His 
arrangement is as follows: 
1. Puccinia Centaureae-vallesiacae Hasler on Centaurea vallesiaca, C. 
alba, C. rhenana and, to a less extent, on C. cyanus. 
2. Puccinia Jaceae Otth on Centaurea Jacea, C. rhenana and, to a less 
extent, on Centaurea austriaca, C. Jacea var. longifolia, C. 
phrygia and C. transalpina. 
