XXIIT.] 



SUMMER RUST AND MILDEW. 



155 



of P. Rubigo-vera, B.C., illustrated in Fig. 69, both en- 

 larged 1000 diameters. The supporting stems of Puccinia 

 graminis, Pers., are larger in proportion, and are accom- 

 panied by no paraphyses 

 in the sori. 



To see the germination 

 of the black Puccinia spores, 

 old Puccinia invaded straw 

 must be looked for in the 

 spring months, and the 

 Puccinia spores must be 

 taken from a pustule with 

 a small knife or needle, and 

 placed in a film of water 

 under a thin cover glass on 

 a slide, and kept in moist 

 air (to prevent evaporation) 

 under a bell glass. Ger- 

 mination usually takes 

 place, as in P. Rubigo-vera, 

 D.C., by the protrusion of 

 a thread from each of the 

 two cells of the Puccinia 

 spore, as illustrated at Fig. 

 81, enlarged 1000 diam- 

 eters. These two threads, 

 the first produced in the 

 spring, are the pro -my- 

 celium, or the first my- 

 celium, of one end of the 

 cycle springing from the X-IOOO" 

 " finishing spores " or tele- FIG. SO. Teleutospores of Puccinia 

 Utospores belonging to the graminis, Pers., as borne in autumn 

 T m1 . ' and winter. Enlarged 1000 dia- 



other end. This pro-my- meterg> 



celium is seen at AA. The 



pro-mycelium proceeds to no great length, but after some- 

 times attaining three or four times the length of the black 



