70 British Uredinece and Ustilagineii. 



en masse, are blackish, but frequently, however, with an 

 olive-brown or yellowish lustre, especially when viewed 

 in an oblique light. U. segetuvi, 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 fonns are specifically distinct. With 

 U. scabiosce the spores in bulk are flesh-coloured, and in 

 U. succisce 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 Ustilaginese are by no means so marked a 

 formation as in the Uredineae. In U. tragopogi the germ- 

 pore is said to occupy from one-quarter to one-half the 

 epispore.* Much more commonly do we find, as in 

 T. tritici,'\ a small opening which splits into a rift as the 

 promycelium grows out. In TliecapJiora liyalina 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. 

 t Brefeld, " Hefenpilze," p. 48. 



% F. von Waldheim, " Sur la structure des spores des Ustilaginees " 

 (1867), pp. 243-245. 



