388 BROOKLYN BOTANIC GARDEN MEMOIRS 
twenty-one species which belong to genera of this subgroup, but was 
able to infect only four species of the genus Taraxacum: T. officinale, 
T. ceratophorum, T. palustre and T. erythrospermum. Three other 
species of this genus tested remained free from the fungus. In many 
of his experiments, Liidi kept control plants of T. officinale and these 
were readily infected by the swarmspores. 
Albugo candida (Pers.) Roussel. Eberhardt (31, 32) has made 
inoculation tests with this parasite. His results are as follows: 
1. Conidia from Capsella Bursa-pastoris infected C. Bursa-pastoris, 
Arabis alpina, Iberis amara and Lepidium sativum. 
Conidia from Capsella Heegeri infected C. Bursa-pastoris and 
Lepidium sativum. 
3. Conidia and oospores from Lepidium sativum infected L. sativum 
and Capsella Bursa-pastorts. 
4. Conidia from Arabis alpina infected A. alpina, A. Halleri, A. 
hirsuta, A. turrita, Capsella Bursa-pastoris, Cardamine pratensis, 
Iberis amara, Lepidium sativum, Senebiera coronopus, but not 
Brassica napus, B. nigra, B. oleracea, Raphanus sativus nor 
Sinapis arvensis. 
5. Conidia from Brassica Rapa infected B. Rapa, B. nigra, B. oleracea 
(var. botrytis, capitata, congyloides), Diplotaxis tenuifolia and 
Sinapis arvensis, but not Capsella Bursa-pastoris, Iberis amara 
nor Lepidium sativum. On the basis of these experiments, 
Eberhardt concludes that there are two specialized races of 
the parasite: 
1. On Arabis-Capsella-Lepidium. 
2. On Brassica-Diplotaxis-Sinapis. 
Melhus (99) has also tested the infecting capacity of Albugo candida 
on the radish (Raphanus. sativus). He was able to infect this host, 
twenty-two varieties being equally susceptible, also Raphanus caudatus, 
Brassica alba (white mustard) and Brassica oleracea (cabbage, fifteen 
varieties). In the case of the latter plants infection was less certain 
than for the radish. The following plants gave negative results: 
Brassica rapa (turnip, ten varieties), B. nigra (black mustard), B. 
campestris (rutabaga, three varieties), Capsella Bursa-pastoris (shep- 
herd’s purse), Lepidium sativum (garden cress), L. virginicum (wild 
pepper grass), Sisymbrium officinale, S. altissimum (hedge mustard), 
Iberis umbellata (candytuft), Nasturtium officinale (water cress) and 
Cheiranthus Cheiri (wall flower). 
Peronospora parasitica (Pers.) de Bary. Gaumann (59) has 
carried out a few experiments with this fungus and finds a high degree 
of host specialization. The fungus that occurs on Capsella cannot 
infect other Cruciferae. The same is true of the race on Brassica. 
tN 
