ORDER UREDINALES (tHE RUSTS) 



403 



Fig. 134. Subclass Teliosporeae, Order Uredinales, Family Melampsoraceae. 

 (A, B) Uredinopsis struthiopteridis Stormer. (A) Urediospore. (B) Section through 

 leaf of host showing uredial sorus with peridium, and teliospores scattered through the 

 mesophyll. (C) P ucciniastrum goeppertianum (Klihn) Klebahn; telial stage in epi- 

 dermis of Vaccinium sp. (A-B, after Dietel: Ber. deut. botan. Ges., 13(7):326-332. 

 C, after Hartig: "Lehrbuch der Baumkrankheiten," Berlin, J. Springer, 1889.) 



with its aecia and spermogonia on the needles of species of Abies probably 

 combines the greatest number of primitive characters of any rust, viz., 

 telial hosts in the ancient group Pteridophyta, colorless urediospores and 

 teliospores, the latter scattered in the mesophyll, uredia surrounded by 

 peridium etc. Two other genera {Hyalopsora and Milcsia) with colorless 

 teliospores formed in the epidermal cells are also found in the ferns. P uc- 

 ciniastrum goeppertianum (Klihn) Klebahn is of interest because it is one 

 of the few rusts in which the sporophytic mycelium is perennial. The aecia 

 occur on the leaves of the fir (Abies) as is true of the other genera men- 

 tioned above. The telial stage (no uredia are known) occurs in Vaccinium, 

 its presence causing the development of a sort of witches' broom with an 

 upright thickened stem and small distant leaves. The mycelium grows out 



