136 DISEASES OF FIELD & GARDEN CROPS. [en. 



and sometimes entails great losses, it may be more con- 

 venient to describe it first. 



The spring rust of wheat appears in March, April, and 

 May, on grasses and cereals : it is common on soft grass, 

 Holcus lanatus, L. ; creeping soft grass, H. mollis, L. ; 

 barren Brome grass, Bromus sterilis, L. ; and wall barley, 

 Hordeum murinum, L. Its specific name, Rubigo-vera, 

 means "true rust." 



If a leaf of wheat invaded by "true rust" be taken 

 in the month of April or May and examined with a strong 

 lens, it will be seen, as on Fig. 62, enlarged three diameters. 



The minute livid yellow 

 pustules are the sori of 

 the Uredo; in the bottom 

 left-hand corner of the 

 illustration a few black 

 spots will be seen, 

 these are the advanced 

 or Puccinia condition of 

 the parasite. If we place 

 a fragment of the leaf 

 under a low power of 

 the microscope and mag- 

 nify twenty -five diam- 

 eters, we shall see the 

 -x-3- pustules as at Fig. 63. 



FIG. 62. Fragment of Wheat leaf in- It is now evident that 

 vacled by Vredo Riibigo-vera D.C. the fungUS within the 



plant has, in reaching 



maturity, burst the epidermis of the wheat leaf. The 

 fungus may be seen as a fine yellowish or orange 

 powder, which is set free by the slightest touch and 

 carried away in the air by the faintest breath. If we 

 now make a transverse section through a very small 

 pustule, cut off a transparent slice from the exposed sur- 

 face, and magnify 200 diameters, we shall see the interior 

 of the pustule as at Fig. 64. This is engraved to the 



