62 British Uvedinee and Ustilaginee. 
Ustilago—The spore-forming hyphe enlarge and 
branch in various ways. The gelatinization of their in- 
terior takes place to such an extent as to almost obliterate 
their lumen, which, however, may frequently be seen as a 
narrow shining line in the middle of the hyphz (Plate V. 
Fig. 7). At certain points the surface of these hyphe en- 
large, so that they appear nodose. The increase in size - 
of the hypha continues, so that adjacent hyphze become 
variously tangled and intertwined together, and eventually 
many of the hyphe appear glued together, or to have 
coalesced. The irregularities of the hyphe become more 
marked, and it is obvious that each tumefaction will even- 
tually become a spore, inasmuch as they gradually get 
more and more rounded (Plate V. Fig. 8). It is in the 
interior of these distended hyphe that spore-formation 
takes place. It is, however, always found that the external 
spores are the most developed, the formation being, in 
fact, centripetal. The commencement of the differentiation 
of the protoplasmic contents is at the exterior of the mass, 
and it gradually proceeds inward towards the centre. The 
spores when first formed have gelatinous envelopes, and 
gradually become more or less polygonal from mutual 
compression. The interior of the spore is now seen to 
have a distinct contour, and to contain fatty granules. 
The outer edge of this contour darkens, and even while it 
is still surrounded by a thin gelatinous envelope the 
irregularities of the epispore begin to be apparent. As 
the spores ripen this gelatinous membrane disappears, so 
that at their maturity they have no remnant of it; nor are 
any remains of the mycelial hyphe attached to them, as is 
often seen in Tilletia. 
Sphacelotheca.—This genus differs from Ustilago in the 
spore-mass being developed in a receptacle. De Bary thus 
describes its development: “The vegetative mycelium, 
