PROTOBASIDIOMYCETES 



405 



resistance being particularly noticeable when the varieties are grown 

 side by side for a period of years. The final effect of the rust 

 upon the plant from year to year is a determining factor in adapt- 

 ability. Sirrine was unable to confirm the observations as to the 

 high resistance of the Palmetto as grown on Long Island, but 

 it is suggested that a weaker strain is there in use. Conover's 

 Colossal and the various forms related to this, or the selections 

 from it, are types of the more susceptible sorts. These, moreover, 

 are the varieties upon which the 

 canning industry depends. The 

 fungus also occurs on some wild 

 species of asparagus such as As- 

 paragus capsicus and Asparagus 

 maritimus. 



The spore forms. No impor- 

 tant distortions are made upon 

 the host by different stages of 

 this fungus. All spore forms 

 are produced on stems and 

 twigs (Fig. 198), and the uredo 

 and teleuto stages occur also 

 on the leaf-like branches. The 

 aecidial stage may appear at 

 almost any point in the United 



States with a growing season no shorter than that of northern 

 New Jersey. The secidia appear in rather long, light green, 

 cushion-like areas. They are short-cylindrical, with a white perid- 

 ium, and the spores appear orange colored from the contents ; 

 the wall, however, is hyaline and granulose. The spores meas-. 

 ure i 5- 1 8 ^ in diameter. They may germinate immediately, and 

 when dry, some at least retain the capacity for germination 

 throughout several weeks. Penetration of the host plant is ap- 

 parently through the stomata. The spermogonia appear in small 

 yellow clusters. 



The uredo or red rust stage appears in early summer, or shortly 

 after the aecidial stage, at first in scattered, deep brown sori, but 

 afterwards the latter may be confluent. The uredospores are yel- 

 lowish brown, with thick walls, fine yellow markings, and provided 



FIG. 199. PUCCINI A ASPARAGI: 

 TELEUTOSPORIC SORUS 



