MILDEWS, RUSTS AND SMUTS 185 
ft Sori not powdery at maturity. 
{a) On stems or leaves. 
Sori pale or brownish. Entyloma. 
Sori broadl}/ expanded, black . . Melanotaenium. 
(b) On roots. 
Forming blackish nodules. Entorrhiza. 
(c) In the fruit. 
Sori enclosed in a membrane formed of hyphae. 
Sphacelo theca. 
II. Teleiitospores aggregated in compact groups forming 
spore-halls. 
* All the spores in a spore-ball of uniform size, and all 
capable of germination. Sori surrounded by a con¬ 
tinuous layer of sterile cells, arranged side by side 
like the palisade cells of a leaf . . . Doassansia. 
Sorus not enclosed in a special envelope formed of 
hyphae ; mostly growing on leaves and stems. 
Tuburcinia. 
Sori rufescent, generally produced in the fruit or seed. 
Thecaphora. 
Sori consisting of spore-balls composed of minute 
spores of equal size and germinating capacity ; other¬ 
wise like Ustilago . Cintractia. 
Sori black, in the flowers of Caryophyllaceous plants. 
Sorosporium. 
** Central cells of the spore-ball dark coloured and capable 
of germination, surrounded by pale coloured sterile 
cells. 
The only genus.. Urocystis. 
NOTES ON THE GENERA 
USTILAGO 
Many of the species are known as " smuts,” forming 
black sooty masses in the ears of wheat, oats, barley, etc. 
Others develop in the anthers of flowers, which produce 
instead of pollen, masses of black powder. Others again 
form black or brown streaks on leaves. All the species are 
parasites, and many select as hosts, grasses and sedges. 
The teleutospores are i-celled, and comparatively minute. 
TILLETIA 
In some instances the spores are produced in the ovary, 
and fill the grain or seed with a mass of blackish spores, 
which in some species has a very disagreeable smell, some¬ 
what resembling stinking fish. Others form streaks on 
