400 PLANT DISEASES 



blackish, hymenium venoso-plicate, 1-3 in. across ; spores 

 reniform, 20-25 X 7-9 /» ; pileus greyish-olive, minutely 

 tomentose. 



Helicobasidium, Pat. — Resupinate, incrusting, soft ; 

 basidia straight at first, then distinctly curved at the apex, 

 with a variable number of transverse septa, bearing 2-4 

 sterigmata from the convex surface of the curved portion ; 

 spores hyaline, continuous, ovoid, often slightly curved. 



Helicobasidium mompa, Tanaka, Jourti. Coll. Sci. Imp. 

 Univ. Japan, vol. iv. pt. i. pi. xxiv.-xxvii. (1891). — Pileus 

 sessile, resupinate, somewhat orbicular or oblong, often 

 irregularly lobed, 5-10 cm. across, 2-4 mm. thick, at first 

 velvety and membranaceous, then subcoriaceous, some- 

 what convex, incrustate, purplish-brown, at length albo- 

 pruinose ; hymenium white ; basidia curved, 1-3-septate, 

 tetrasporous ; sterigmata elongated ; spores ovoid, curved, 

 hyaline, 10-12X5-7 /*. 



USTILAGINACEAE 



Mycelium parasitic in the tissues of living plants, abun- 

 dant, but soon disappearing ; teleutospores formed in the 

 interior of hyphal branches, which often become gelati- 

 nous ; spores on germination producing a continuous or 

 sparingly septate promycelium, which bears secondary 

 spores. Secondary spores either producing a delicate 

 germ-tube, or bearing conidia, which often reproduce 

 themselves by gemmation. 



Ustilago, Pers. — Vegetative mycelium spreading in the 

 tissues of the host, soon disappearing ; spore producing 

 hyphae branched, the spores formed in the interior of 

 gelatinised, clustered terminal branches; spores i-celled, 



