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ON A FJJl^am-OVULABIOPSIS PAPAYJE, N. SP.— WHICH 
CAUSES POWDEEY MILDEW ON THE LEAVES OF THE 
PAWPAW PLANT (CABICA PAPAYA, LINN.). 
By Paul A. van der Bijl. 
(With Plate X and one Text-figure.) 
Along the coast of Natal, where the pawpaw is generally cultivated, we 
frequently find the under-surface of their leaves showing white powdery 
areas (Plate X) . This is due to the growth of a fungus which may at times 
cover the greater portion of the under-surface of the leaves. The mycelium 
of the fungus creeps on the surface, and branches of the hyphae penetrate 
through the stomata and ramify in the intercellular spaces of the spongy 
parenchyma tissue of the leaves. 
A " powdery mildew " does not appear to have been previously reported 
from the leaves of the pawpaw, and this fungus is held to be a new species, 
for which the name Ovulariopsis pa])ayae, n. sp., is suggested. The genus 
Ovulariopsis was founded by Patouillard and Hariot'" in 1900, and is 
characterised by the following description : Sterile hyphae epiphytic and 
intercellular ; fertile arising from sterile, erect, simple, bearing at their 
apices a single, large, hyaline, subclavate conidium. 
In its subclavate conidia and having the sterile hyphae both epiphytic 
and intercellular the genus Ovulariopsis resembles the genus PhyUactmia, 
Lev., which latter belongs to the Erysibaceae — a family including a number 
of fungi responsible for " powdery mildews." 
Ovular io2:> sis and Phyllactinia are on conidial fructifications and habit 
evidently closely related, and the former may be in part only the conidial 
fructifications of the latter. 
Thus far only the conidial stage has been observed in the pawpaw 
fungus, and should the perithecial stage subsequently come to light and 
prove to belong to Phyllactinia then this name would replace Ouulariopsis, 
as it would represent the perfect stage in the life-cycle of the fungus. 
Salmou,t basing his conclusions on the size of the conidia, considers 
* Patouillard, N., and P. Hariot, " Enumeration des Champignons recoltes par 
M, A. Chevalier au Senegal et dans le Soudan occidentale," ' Journ. de Botanique," xiv, 
p. 245 (1900). 
t Salmon, E. S., "On the Identity of Ovulariopsis, Pat. and Har., with the 
Conidial Stage of Phyllactinia, Lev.," 'Ann. Myc./ ii, p. 438 (1904). 
