MILDEWS, RUSTS AND SMUTS 
13 
sterile ; the remainder shortly cylindrical, or cuboid, wall 
colourless, thin, with a thickened central, or equatorial 
zone, producing zoospores on germination, 18—23 p diam. ; 
oospore globose, yellowish-brown, markings somewhat 
variable, and not strongly pronounced, with a raised net¬ 
work having spines springing from the ridges, and minutely 
warted on the areas included by the network, or with rather 
large, hollow warts, which in turn are minutely warted, 
45—65 (J. diam. 
Syn. Cystopus cubicus, Lev. 
Cystopus spinulosus, De Bary. 
On both surfaces of living leaves of Goats’-beard {Trago- 
pogon pratensis), and many other plants belonging to the 
order Compositae. 
PHYTOPHTHORA, De Bary 
Mycelium branched, running between the cells of the 
host-plant, and giving off slender haustoria which enter 
the cells ; conidiophores solitary or in clusters, emerging 
through the stomata, or bursting through the epidermis, 
simple below, becoming variously branched above, some¬ 
times forking ; conidia elliptical, tip papillate ; producing 
zoospores on germination, the conidia are produced at the 
tips of the conidiophores, but after the formation of a 
conidium, the conidiophore increases in length, and again 
bears a conidium at its tip ; the conidiophores becoming 
swollen or knotted at the point of origin of each conidium ; 
oospores globose, smooth, coloured. 
Recognised by the knotted appearance of the upper por¬ 
tion of the conidiophores in P. infestans, the knots or swel¬ 
lings corresponding to the point of origin of conidia. In 
some instances a conidium persists after the conidiophore 
has grown out above it, and consequently appears as if it 
had originated laterally on the conidiophore. 
KEY TO THE SPECIES 
infestans. Conidiophores knotted towards the tip. Para¬ 
sitic on plants belonging to Solanaceae. 
omnivora. Conidiophores not knotted towards the tip. 
Parasitic on plants belonging to various orders, Cras- 
sulaceae, Cactaceae, Cupuliferae, etc. 
[phaseoU, Thaxt. Conidiophores knotted towards the 
tip; conidia on germination sometimes producing 
zoospores, at others a promycelium. Parasitic on 
plants belonging to Leguminosae {Phaseolus).'] 
