XXI.] 



SPRING RUST AND MILDEW. 



137 



same scale as Pucdnia mixta, Fl., Fig. 13, which may be 

 referred to for comparison. 

 The yellow powder is now 

 seen as a mass of yellowish 

 sub-spherical or ovoid spores, 

 each spore filled with dense 

 granular protoplasm, is sup- 

 ported on a short stalk and 

 springs from an involved 

 stratum of mycelium. A single 

 spore is seen emerging through 

 the centre of a ruptured pus- 

 tule at A. The transparent 

 circles at BB are part of the 

 cellular tissue of the wheat 

 leaf. When the spores escape 

 in this matter, as they do in 

 inconceivable numbers, many 

 fall on to the leaves from 

 which they have grown. In 

 their new position they germi- 

 nate, as at Fig. 65, by the protrusion of a spawn-thread 

 from both sides, the vital material pours from the spore 



11 



X 25 



FIG. 63. Pustules or Sori of Uredo 

 Bubigo-vera, B.C., on Wheat 

 leaf. Enlarged 25 diameters. 



r 



FIG. 64. 



Transverse Section through a pustule or Sorus of Uredo Rubigo-vera, D.C. 

 Enlarged 200 diameters. 



into the threads ; and as the spores get empty a septum 

 appears as at A, and cuts off the connection of the germ- 

 tube with the spore. The germinal threads now 



