IOWA ACADEMY OF SCIENCE 
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On Ulmus racemosa all I have found has been in circumscribed 
patches on the upper surface of the leaf. These patches are often 
very conspicuous. 
Uncinula clintoni Peck. 
Uncinula clintoni Peck. Hitchcock, Partial List Iowa Powdery Mildews; Fink, 
Blights, etc., of Fayette. 
Hypophyllous or amphigenous, mycelium usually more or less evanescent; 
perithecia gregarious or scattered, 80-130 micra in diameter, cells irregular in 
shape, 10-20 micra wide; appendages 10-35, 1-2% times the diameter of the 
perithecium, hyaline or somewhat colored at base; apex clavate uncinate; asci 
4-10, very short stalked, 40-62x34-40 micra; spores 3-7, 20-27x10-13 micra. 
On Tilia americana L. Ames, Sept. 22, 1878 (Bessey) ; 1878 (Thomas) ; 
Sept., 1892 (Bettinger) ; * Cedar Rapids, Sept., 1886 (Hitchcock); Decorah, 
Aug., 1879 (Holway) ; *Fayette, 1893 (Fink) ; Johnson Co., Sept. 14, 1886 
(Macbride) ; Jones Co., Aug., 1895 (Macbride) ; Muscatine, Oct. 20, 1900 
(Stromsten) . 
Uncinula geniculata Gerard. 
Epiphyllous; mycelium thin; forming definite patches or more or less ef- 
fused, sometimes evanescent; perithecia subgregarious or scattered, 90-120 
micra in diameter, cells rather irregular, 10-15 micra wide; appendages 24-46, 
l %-2 times the diameter of the perithecium, some usually abruptly bent or 
geniculate, hyaline, aseptate, apex simply uncinate; asci 5-8; very short pedi- 
cellate, 48-56x34-38 micra; spores 4-6, 22x12 micra. 
On Moms rubra L. Decatur Co., Oct. 28, 1905 (Anderson) . 
This species is very inconspicuous and may be much more common than 
would be indicated by the fact that it is not often collected. 
Phyllactinia Lev. 
Perithecia large; asci many; 2, rarely 3-spored, appendages hyaline, free 
from the mycelium, acicular or rarely flexuously bent, acute at tip with a 
bulbous base; apex of perithecium provided with outgrowths from the epider- 
mal cells. This genus is often separated from the others as a subfamily 
(Phyllactinicae) . This distinction is based on the fact that the mycelium does • 
not form haustoria in the ordinary manner, but sends special branches into 
the stomata of the host, each of these branches giving rise to -an haustorium 
which penetrates the surrounding tissue. 
Key to Iowa Species of Phyllactinia. 
Appendages undivided 1. P. corylea 
Appendages divided 2. P. corylea tomentosa 
Phyllactinia corylea (Pers.) Karst. 
Phyllactinia condollei Lev. Bessey, The Erysiphei. 
Phyllactinia guttata (Wallr.), Lev. Bessey, The Erysiphei. 
Phyllactinia suffulta (Rebent.), Sacc. Bessey, Prel. List. Ames Flora; Hitch- 
cock, Partial List Iowa Powdery Mildews; Fink, Blights, etc., of Fayette. 
