a 
REED: SPECIALIZATION OF PARASITIC FUNGI Shed 
has succeeded in producing aecidia on twenty-two species, belonging 
to fifteen genera, distributed among six different families, as follows: 
1. Polygonaceae: Polygonum aviculare, P. erectum and P. ramosissi- 
mum. 
2. Chenopodiaceae: Salsola pestifer, Chenopodium album, C. glaucum, 
C. lanceolatum, C. pagonum, Monolepis nuttaliiana and Kochia 
scoparia. 
Amaranthaceae: Amaranthus retroflexus and A. blitoides. 
Nyctaginaceae: Abronia fragrans. 
Cruciferae: Capsella Bursa-pastoris, Lepidium densiflorum, L. 
medium, Erysimum asperum, Sophia pinnata, Roripa palustris, 
Thaspi arvense and Sisymbrium altissimum. 
6. Capparidaceae: Cleome serrulata. 
It is also suggested that species of Papaveraceae may be aecidial 
hosts for the same rust. 
Bock (19) has carried out rather extensive cultural tests with 
Puccinia Gentianae (Str.) Link. He reports no evidence for host 
specialization, finding that a large number of species of Gentiana were 
readily infected with rust from two different species. 
Another illustration of the same condition is reported by Camilla 
Popta (109) who has been able to infect a number of umbellifers with 
the same race of Protomyces macrosporus. The following plants were 
infected with the fungus from Aegopodium podograria: Cicuta virosa, 
Seseli montanum, Libanotis vulgaris, Palimba chalrau, Bubon gemmif- 
erum, Pachypleurum alpinum, Bunium virescens, Ferula_ thyrstflora, 
Trinia vulgaris and Athamanta cretensis. 
If now we compare the degree of specialization found in the 
different parasitic fungi we find the greatest divergences. Ina general 
way the specialized races may be grouped on the basis of their host 
range as follows: 
I. Specialized races restricted to certain species of a genus of 
hosts. Here belong the specialized races of Erysiphe graminis within 
the genera Bromus and Hordeum; of Puccinia dispersa within the 
genus Bromus; the specialized races of Phragmidium disciflorum, 
Puccinia Centaureae, P. Epilobii-tetragoni, P. Helianthi, P. Hieracii, 
P. Pulsatillae, P. Ribis, P. Ribesti-Caricis, P. Caricis-montanae, 
Uromyces Poae, U. proeminens and Melampsora Euphorbiae. 
2. Specialized races restricted to a particular genus of host plants. 
A number of specialized races of this sort are known. Among the 
Erysiphaceae we find the specialized races of Erysiphe graminis on 
Agropyron, Dactylis, Poa and Secale and of Erysiphe cichoracearum 
on Aster and Solidago. Among the rusts we find the races of Puccinia 
graminis on Aira, Poa, Calamagrostis and Apera; of P. coronata on 
on —& Ww 
