50 FUNGOID DISEASES 



utilizes but probably does not require two host plants 

 on which to complete its life cycle (see p. 51). 



The reddish-yellow pustules above mentioned are 

 due to the fungal threads breaking through the 

 epidermis and bearing the orange-coloured spores 

 called uredospores (Fig. 13, B). These are the 

 summer spores ; they are thin walled, light coloured, 

 and one celled, and are easily carried by the wind 

 to healthy wheat plants, on the leaves, leaf sheaths, 

 and stems of which they germinate. They send out 

 a oferm tube which enters and ramifies within the 

 tissues, branches and rebranches, finally breaking 

 through the surface and producing the yellow 

 pustules. 



The darkening of the pustules is due to the for- 

 mation of another kind of spore — teleutospore or 

 teliospore — from the same mycelium (see Fig. 13, B). 

 These teleutospores are longish oval, two celled, and 

 have a thick outer wall They are borne on a stalk 

 about the same length as the spore, and rest over 

 winter. In the spring they germinate, each cell 

 sending out a hyphal thread which branches at the 

 tip and forms four sterigmata, on each of which a 

 conidium (sporidium or basidiospore) appears. This 

 basidiospore appears to be incapable of infecting the 

 wheat plant, but it is able to penetrate the leaf of 

 the barberry [Berberis vulgaris), develop within, 

 and in a short time produce small flask-shaped bodies 

 called spermogonia on the upper surface of the leaf. 



