Formatio}i of Tcletitospores of Ustilagincar. /r 



of mutual compression by being flattened in one or more 

 directions. In U. caricis they are often flattened on one 

 side, so as to be subhemispherical. In size they vary 

 from 4^ in U. Jiypodytcs to 30/.* or more in Urocystis fischeri. 

 They may be simple or collected into spore-balls (Soro- 

 sporium), in which case they appear, when seen separately, 

 as in T. hyalina, to be segments of a sphere, being convex 

 externally, but internally more or less wedge-shaped. In 

 Urocystis the spore-balls are surrounded by a variable 

 number of barren spores or pseudospores, which are paler 

 in colour, often almost hyaline ; these do not germinate. 



Hartsen * found that the spores of the U. Diaydis would 

 not yield their colouring matter to any of the ordinary 

 solvents, but that strong sulphuric and nitric acids de- 

 colourized the epispore, rendering it more transparent 

 without at once destroying it, so that the contour of the 

 exterior remains unafl"ected. Although the spores some- 

 times burst, yet by these reagents the structure of the 

 epispore can be conveniently examined. In nitric acid 

 the spores of the U. Diaydis swell up, and after a time 

 they dissolve, giving off an odour of bitter almonds. Sul- 

 phuric acid is the better reagent to employ in the exami- 

 nation of the spores, as, although it decolourizes and renders 

 the epispore transparent, yet it does not so rapidly 

 destroy the latter. 



* Hartsen, "Compt. rendus " (1874), pp. 441, 442. 



