ORDER UREDINALES (tHE RUSTS) 407 



compound teliospores which escape from the sorus dry or embedded in 

 sHme. Aecia only very exceptionally on Pinaceae. The stalked forms of 

 this family are easily distinguished from the Melampsoraceae but the 

 forms with tehospores produced in loose, quickly fragmenting chains are 

 a sort of connecting group difficult to segregate definitely from one or the 

 other family. Dietel (1928) recognized 83 genera and about 3000 species, 

 while some authors add at least 20 genera by the segregation of such 

 larger genera as Uromyces and Puccinia. These two are among the more 

 important genera of the family with, respectively, about 600 and over 

 1800 species. The location of the spermogonia is of importance taxonomi- 

 cally. They are subcuticular and rather flattened or subepidermal and 

 then more spherical. The uredia may have paraphyses or these may be 

 lacking. The aecia may be cupulate, or cornute, or hyphoid, or caeomoid, 

 or uredioid. The teliospores may be single on the pedicel {Pileolaria, 

 Trachyspora, Mainsia, Uromyces) or several on one pedicel (compound 

 teliospores). In Puccinia there are two; in Phragmidium, Xenodochus, etc., 

 three to many in a single row on the simple pedicel. In Ravenelia the telio- 

 spores are numerous in a head on a usually compound pedicel, being sub- 

 tended by hyaline "cysts." As in the Melampsoraceae many species are 

 autoecious and long-cycled, others are heteroecious, and many lack one or 

 more spore forms. In the case of Puccinia and Uromyces the relationship 

 is very close. The spermogonia are subepidermal, the aecia are cupulate 

 and the uredia are without peridium with urediospores single on long 

 stalks, in both genera. The teliospores are brown and stalked, emerging 

 from a ruptured epidermis. In Uromyces they are simple, in Puccinia 

 compound, formed of two teliospores closely united in a row with a one- 

 celled stalk. A number of cases are known where the aecia of heteroecious 

 species of the two genera are borne on the same host and the urediospores 

 and teliospores on the same alternate host, the aeciospores and uredio- 

 spores of the respective species of Uromyces and Puccinia being practically 

 indistinguishable. The only essential difference is that in the one genus 

 the pedicel is topped by a single teliospore and in the other by two. 

 Arthur (1934) believes that the frequency of such cases indicates a very 

 close relationship of the two genera. In some species of Puccinia, inter- 

 mingled in the same sorus may be found a varying number of Uromyccs- 



FiG. 136 — {Continued) 



(D) Dicheirinia binata (B. & C.) Arth. (E) Prospodium plagiopus (Mont.) Arth. (F) 

 Ravenelia acaciae-micranthae Diet. (G) Section through portion of tehum of Goplana 

 dioscoreae (B. & Br.) Cummins. (A, after Engler and Prantl: Die Xatiirlichen Pfianzen- 

 familien, Leipzig, W. Engelmann. B, after Sappin-TroufTy: Le Botaniste, 5:59-244. 

 C, courtesy, Cummins: Mycologia, 23(6):433-445. D, courtesy, Cummins: Mycologia, 

 27(2):151-159. E, courtesy, Cummins: Lloydia, 3(l):l-78. F, after Dietel: Botan. 

 Centr. Beihefte, Zweite Abt.^, 20 :SA3-4\3. G, courtesy, Cummins: Mycologia, 27(6) :605- 

 614.) 



