MILDEWS, RUSTS AND SMUTS 
39 
being branched in a definite manner at the tip, and in not 
originating from the base of the perithecium. 
KEY TO THE SPECIES 
Appendages of two kinds, one kind springing from the tip 
of the perithecium, long, and generally unbranched ; 
a second kind springing from the base of the perithe¬ 
cium, and only slightly differing from the mycelium. 
leucotricha. 
Appendages springing more or less equatorially from the 
perithecium, 2—^4 times forked at the tip, tips of the 
ultimate branchlets swollen .... oxyacanthae. 
Appendages springing from the tip of the perithecium, 
very long, wavy, tips 2—3 times forked, branchlets 
recurved.. schlechtendalii. ‘ 
Podosphaera oxyacanthae, De Bary. Growing on both 
sides of the leaves, mycelium sometimes forming persistent 
white patches, at others soon disappearing; perithecia 
crowded or scattered, 64—90 p diam. ; appendages spread¬ 
ing, originating more or less equatorially, or nearer to the 
top of the perithecium, very variable in number and length, 
4—30 in number, and from i—10 times as long as the dia¬ 
meter of the perithecium, base brownish, tip 3—4 times 
forked, ultimate branchlets knobbed at the tip ; ascus very 
broadly pear-shaped, or subglobose, 58—90 x 45—70 p ; 
spores normally 8, sometimes fewer, variable in size, 18—30 
X 10—17 p. 
Syn. Erysiphe oxyacanthae, D.C. 
Podosphaera myrtillina, Kze. and Schm. 
Podosphaera clandestina, Lev. 
Parasitic on plants belonging to Rosaceae and to Erica¬ 
ceae, diS Crataegus, Amelanchier, Prunus, Spiraea, Vaccinium 
etc., var. tridactyla (Wallr.). Perithecia 70—150 p diam. ; 
appendages 2—-8, usually about 4, i—^8 times as long as 
the diameter of the perithecium, from the top of which 
they spring in a tuft, and are more or less erect, 3—5 times 
forked at the tip, ultimate branchlets knobbed. 
Differs from the typical form in the few appendages 
springing in a cluster from the top of the perithecium, and 
in being more or less erect. 
Syn. Alphitomorpha tridactyla, Wallr. 
Podosphaera kunzei. Lev. 
Parasitic on species of Prunus, Pyrus, and Spiraea, 
