MILDEWS, RUSTS AND SMUTS 
21 
Meum at amanticum, also on plants belonging to the fol¬ 
lowing genera. 
In many plants the mycelium of the fungus is perennial 
in the root, and grows up with the above-ground parts 
year by year. 
BREMIA, Regel 
Mycelium branched, swollen here and there, running 
between the cells of the host-plant, and sending small, 
vesicular haustoria into the cells ; conidiophores generally 
tufted, erect, repeatedly forking upwards, the terminal 
branchlets ending in a more or less circular, concave disc, 
from the margin of which spring short processes bearing 
the broadly elliptical, colourless conidia ; oospheres sub- 
globose, with a thick wall; oospores pale yellow, globose. 
Readily distinguished from all other genera by the pecu¬ 
liar flattened disc at the tips of the branchlets, from which 
the conidia spring. 
Only one species known. 
Bremia lactucae, Regel. Forming yellowish-green ex¬ 
pansions on the upper surface of the leaf, the corresponding 
parts of the under surface, more or less, covered with a very 
delicate, white mildew ; conidiophores originating either 
singly or in tufts, erect, rather rigid, 300—600 X 10—12 (x, 
repeatedly forking above, or* the branches rarely in threes, 
the ultimate branchlets bearing a more or less circular, 
saucer-shaped body, from the edge of which spring several 
short projections, each bearing a conidium ; conidia broadly 
elliptical, or almost globose, with a large flattened wart 
at the tip, colourless, 15—24 X 15—24 [x ; oosphere glo¬ 
bose, wall thick, yellowish ; oospore globose, pale yellow 
or brownish, often wrinkled, 25—35 [x. 
Syn. Botrytis lactucae, Unger. 
Botrytis ganglioniformis, Berk. 
Peronospora ganglioniformis, De Bary, 
Parasitic on the leaves of plants belonging to the order 
Compositae, as species of Lactuca, Senecio, Helichrysum, 
Cirsium, Centaur ea, Lapsana, Leontodon, Tragopogon, 
Hypochaeris, Mulgedium, Sonchus, Crepis, Hieracium, etc. 
It is very destructive to cultivated lettuce {Lactuca 
scariola, var. sativa), more especially when grown under 
glass, and in a damp atmosphere. 
PERONOSPORA, Corda 
Mycelium branched, swollen here and there, haustoria 
generally slender and branched, rarely vesicular or pear- 
