408 CLASS BASIDIOMYCETEAE 



like teliospores ("mesospores") among the typical compound teliospores. 

 In Phragmidium the row of teliospores is longer, three to eight or more in 

 a row, and the stalk is long and enlarged toward the base. In Gymnospo- 

 rangium (with 40 or more species) the stalks are very long and their walls 

 as well as the outer walls of the usually two-celled compound teliospores 

 swell when wet so that the masses of teliospores are extruded from the 

 telial galls as gelatinous tongues sometimes 2 to 3 cm. in length. The aecial 

 hosts of this genus with a few exceptions belong to the Malaceae and the 

 telial hosts are species of Juniperus or closely allied genera. This genus 

 forms rather an exception in that it is the dicaryon stage that is perennial, 

 the galls on the host persisting sometimes for several years. In Dicheirinia 

 two, rarely three, verrucous teliospores are borne side by side at the apex 

 of a common pedicel whose upper cell is divided into two or three short 

 cells from which the teliospores arise. Prospodium, like Puccinia, has two 

 teliospores in a single row but they differ in minor points. Goplana is some- 

 times placed in this family because of its stalked spores. These grow up 

 into a gelatinous matrix and, in the manner of Coleosporiinn produce an 

 internal promycelium. Ravenelia is a genus whose tehospores form a head 

 of one layer of fertile spores subtended by colorless cysts which possibly 

 represent sterile tehospores. The head is supported by a centrally attached 

 stalk usually several cells in thickness. The species of this genus are 

 mostly tropical and subtropical and are autoecious so far as known. 

 Gymnoconia resembles Puccinia in its two-celled compound teliospores 

 but the aecia are diffuse (i.e., caeomoid) without peridium, and the 

 spermogonia are subcuticular. Urediospores are lacking. (Fig. 136.) 



In addition to the genera and species assigned to these two families 

 there are over 1000 species of which the telial stage is unknown or its 

 connection with the other stages not determined. Peridermium, Aecidium 

 (600 species) and Caeoma represent different types of aecia. Uredo (450 

 species) consists of species of which the uredial stage only is known. In 

 most of these cases there are probably other stages as yet unknown or 

 whose connection with these has not yet been demonstrated, but it is 

 possible that in some of these species the other stages have been omitted 

 during the course of evolution. 



The Uredinales are of great economic interest on account of their 

 harmful effects on many important crops. The following may be men- 

 tioned since they frequently cause great damage on small grains: Puccinia 

 graminis Pers., several varieties on wheat, rye, oats, barley; P. ruhigo-vera 

 (DC.) Wint., several varieties on wheat, barley, rye; P. coronata Corda, on 

 oats; P. glumarum (Schm.) Erikss. & Henn., on wheat, rye, barley; P. 

 sorghi Schw., on corn (maize); Gymnosporangium juhiperi-virginianae 

 Schw., on apple; Tranzschelia pruni-spinosae (Pers.) Diet., on peach; 

 Gymnoconia peckiana (Howe) Trotter and Kunkelia nitens (Schw.) Arth., 

 on Ruhus spp.; P. asparagi DC, on asparagus; Uromyces phaseoli typica 



