32 British Uredinece and UstilaginetE. 



spores in the spore-bed. Whether this be the simple 

 passive process we have hitherto regarded it or not is 

 undetermined. It is quite possible that it may be aided by 

 a projective force, as Brefeld * has shown in the Agaricini. 

 In them the basidia become by degrees fuller of protoplasm, 

 until a certain state in the tension of the elastic walls takes 

 place. When this has attained its full extent, the upper 

 part of the basidium, immediately below the spore, gives 

 way and becomes split off all round, the spore being 

 projected from its sterigma at the point of its attach- 

 ment. A similar process occurs in Pilobolus, only in this 

 case the rupture is lower down, and not at the exact point 

 of junction of the spore with its basidium. 



As soon as each uredospore is ripe it is capable of germi- 

 nating, and when placed in a sufficiently damp environment 

 it does so in a few hours. This process is accomplished in 

 the same manner as has been already described under the 

 secidiospores. It consists in the protrusion of a germ-tube 

 through one or more of the germ-pores, which branches, 

 elongates, circumnutates, and receives the protoplasm from 

 the interior of the spore, and passes it onwards to its peri- 

 pheral extremity (Plate III. Figs, ii, 12, 13). In the 

 same way its extremity, or the extremity of one of its 

 branches, enters into one of the stomata of the host-plant, 

 and in its tissues develops a fresh mycelium (Plate III. 



Fig. 15)- 



Under certain circumstances, when the germ-tube 

 cannot enter a stoma, instead of growing in the mode 

 described, it dilates in a bulbous manner f at its extremity 

 into a spherical dilatation, into which the orange granules 

 accumulate ; or it may give off one or more lateral out- 



* Brefeld, " Schimmelpilze. " 



t Plowright, "Germination of Uredines ; " "Grevillea," vol. ix. pi. 

 159, figs. 10, II, 12. 



