138 DISEASES OF FIELD & GARDEN CROPS. [en. 



the organs of transpiration of the leaf, and there form a 

 new stratum of mycelium, from which new Uredo pustules 

 arise. Under favourable circumstances this growth and 



X-IOOO 



FIG. 65. 



Germinating spore of Uredo Rubigo-vera, D.C. 

 Enlarged 1000 diameters. 



regrowth of successive crops of spores goes on for several 

 weeks, until the whole plant, whether wheat, rye, or some 

 wild grass, is at length permeated by the spawn. 



The above -described condition of spring rust is the 

 same with Uredo Rubigo, D.C., Uredo Rubigo-vera, Lev., 

 Coeoma Rubigo, Lk., Trichobasis Rubigo-vera, Lev., and 

 Trichobasis glumarum, Lev. 



As the autumn and winter approach, the pallid and 

 yellowish spots of the Uredo vanish, and black spots 

 appear, and this black condition is the mature fungus of 

 the mildew named Puccinia Rubigo-vera, D.C. A small 

 piece of wheat-stem is illustrated, enlarged five diameters, 

 at Fig. 66, the small black dots show the Puccinia 

 pustules. Reference may be here made to Fig. 12, where 

 similar pustules are shown, to the same scale, on a frag- 

 ment of a flower stem or scape of chives. The black sori 

 are farther enlarged to twenty-five diameters at Fig. 67, 

 to show that the pustules are almost identical in appear- 

 ance with the Uredo sori of Fig. 63 ; the only difference 



