Formation of Teleutospores of Ustilaginee. 69 
Localization of Spore-beds.—The bulk of the Ustilagineze 
are characterized by the constancy by which they repro- 
duce their spore-formation, in the same tissues of their 
respective host-plants. In the majority of the species the 
spores are localized somewhere in the reproductive organs 
of the host-plant ; very frequently in the ovary (T72U/etia 
tritict, decipiens, U. caricis, Thecaphora hyalina), or in the 
anthers (VU. violacea, scabiose@) ; often the blossoming and 
fructifying organs are attacked and destroyed (U. segetum, 
bromivora, kiihneana, Sphacelotheca); sometimes the leaves 
are affected (U. longissima, T, strieformis, Uroc. occulta), or 
the stems (U. hypodytes, grandis), or even the subterranean 
organs (U. hypogaea, Uroc. gladiol). With Entyloma and 
its allies, however, this selection of tissue by the parasite 
does not obtain; with these species the spore-formation 
seems to occur in almost any part of the plant. 
Structure of the T: eleutospores.—The teleutospores of 
the Ustilaginez consist of two membranes: an outer, which 
is thick and generally dark-coloured—the exospore; and 
an inner, which is thin and hyaline—the endospore, The 
exospore is subject to considerable variety; it may be 
quite smooth, or covered with extensive reticulations. 
Between these various intermediate conditions occur ; thus 
in U. segetum it has generally been regarded as smooth, 
but it is rather to be described as granular, although Winter 
speaks of it as being “generally very minutely verrucose, 
and seldom quite smooth.” The degree of roughness of 
the epispore varies from extremely minute elevated points 
to marked tubercles. These elevations may be evenly 
distributed over the whole spore, or they may be confluent 
in lines or ridges. Sometimes these ridges anastomose, 
and so form a reticulate or alveolate spore (7. ¢rzticz, 
Sphacelotheca). The colour of the spore depends upon that 
of the exospore; as a general rule the spores, as seen 
x 
