70 British Uredinee and Ustilaginee. 
en masse, are blackish, but frequently, however, with an 
olive-brown or yellowish lustre, especially when viewed 
in an oblique light. UT. segetum, when it occurs in wheat, 
has a distinctly golden lustre, but when on Avena elatior 
it is sooty black. Physiological research will possibly 
show that these two forms are specifically distinct. With 
U. scabtose the spores in bulk are flesh-coloured, and in 
U. succise they are quite white. Individually, the spores 
of the various species, as seen under the microscope, afford 
a considerable range of colour—black, dark violet, brown, 
olive-brown, and yellowish, or quite colourless. In some 
species a germ-pore is said to exist, through which the 
promycelium is protruded in germination ; but these germ- 
pores of the Ustilaginez are by no means so marked a 
formation as in the Uredinee. In U. tragopog? the germ- 
pore is said to occupy from one-quarter to one-half the 
epispore.* Much more commonly do we find, as in 
T. tr¢tic?,} a small opening which splits into a rift as the 
promycelium grows out. In Thecaphora hyalina the germ- 
pore is round and paler in colour than the rest of the 
epispore ; moreover, it is smooth, while the epispore is 
verrucose. Upon the whole, although germ-pores probably 
exist in all species, they are inconspicuous, and are very 
easily overlooked in the smaller spores. The reticulations 
on the epispore of Sphacelotheca are shown by the action 
of sulphuric acid, when examined: by a high magnifying 
power, to consist of a series of distinct palisades, placed 
vertically.{ As a general rule, the spores are globose, but 
in most species this is subject to a certain amount of 
variation ; they often have one diameter rather longer 
than the other, but more frequently they show the result 
* De Bary, ‘* Morph. und Physiol.,” p. 128. 
+ Brefeld, ‘‘ Hefenpilze,” p. 48. 
{ F. von Waldheim, ‘Sur la structure des spores des Ustilagingées ” 
(1867), pp. 243-245. 
