Friesia X, 4-5

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leaves tend to die off earlier than non-infected older leaves. After
heading spots may occur on glumes and awns (Fig. 3). Pycnidia which
develop in the lesions are frequently followed by perithecia in late
summer. In some stages of development the symptoms may be mistaken
for those caused by Rhynchosporium secalis from which they, however,
are readily distinguisable by the presence of pycnidia.
MORPHOLOGY AND GROWTH CHARACTERISTICS
OF THE PATHOGEN IN CULTURE
Pycnidia occur in affected barley tissue from May throughout the
growing-season. The pycnidia are subepidermal, spherical, at first
translucient, later becoming dark brown, 78-182 u , The ostiole is a
F ig. 3. Leptosphaeria nodorum. Ears of barley naturally infected. The
lesions on glumes and awns contained numerous pycnidia. Collected on
July 27th.
circular to oval opening. Pycnospores (Fig. 4) are cylindrical, rounded
at the ends, hyaline, with 1-3 (usually 3) septa, measuring 17-28 X
2.8-4.0/-l (average 23 X 3.2 u , 100 measurements in water).
In the years 1971-73 perithecia were found abundantly on infected
leaf blades and sheaths just before harvest and on stubble and stems