EUTHALLEPHYTA EUMYCETES RUSTS 229 



Common speedwell is a very common weed in St. Louis and other parts of 

 Missouri and southern Illinois, but so far as known, the aecidium has not 

 been found on these weeds. 



Pttccinia dispersa. Eriks, & Hen. 



This species of rust is apparently very common in Europe. There are 

 three different stages. The aecidium stage produces circular or elongated, 

 somewhat swollen, spots on the leaves, petioles and stem of several members 

 of the borage family. The spores are between 20 to 30 /* or 20 to 30 /* x 19 to 

 22 /* in diameter. The teleuto spores long remain covered by the epidermis. 

 The sori are chambered, surrounded by numerous brown paraphyses; spores 

 are mostly club-shaped, unsymmetrical and 40 to 50 M long. 



Pucdnia coronata. Cda. Crowned Rust 



The aecidium produces round or elongated spots with elongated, conspicu- 

 ous aecidia; the spores from 18 to 25 M x 14 to 19 /*; the uredosori are long, 

 confluent, mostly on the upper surface of the leaf; they are orange-colored, and 

 are soon exposed, each pustule containing a large number of 1-celled sub- 

 globose, roughened spores which are spherical or short-elliptical; the uredo- 

 spores are yellow, 20-32 /* in diameter by 28-32 x 20-24 /*. The teleutospores 

 remain covered by the epidermis, and in this respect they resemble the covered 

 rust of wheat (Pucdnia glumarum}. They usually occur on both sides of the 

 leaf. The spores are short-stalked, cuneate and more or less truncate above, 

 crowned with several projecting horns. 



Distribution and hosts. Common wherever oats is cultivated and in several 

 of its forms it occurs upon cultivated grasses. This is a well known destructive 

 rust of oats and several other grasses and has received considerable attention 

 from early mycologists. Klebahn has recently described this rust under several 

 distinct forms. The P. coronata dactylidis in a narrow sense includes the rust 

 upon Dactylis glomerata or orchard grass, Festuca sylvatica with aecidia on 

 Rhamnus frangula and P. coronifera. 



Ericksson and Henning distribute these forms into P. coronata I, and P. cor- 

 onata II. Historically this rust is of considerable importance, since Gmelin 

 was familiar with this disease in 1791, and described it as Aecidium Rhamni on 

 Rhamnus. The aecidium stage occurs on species of buckthorn (Rhamnus) 

 especially (R. cathartica and R. Frangula). In Iowa an aecidium is frequently 

 found on a native buckthorn (R. lanceolata), but its connection with this host 

 has not been studied. The aecidium attacks not only the leaves, but occurs 

 on mid-vein, petiole, pedicels and flowers. As a result of the attacks, distorted 

 leaves and flowers are produced. 



Pucdnia sorghi. Schw. Maize Rust 



Uredo and teleutosori upon the leaves and bracts; the former small, light 

 brown sori, soon rupturing the epidermis; teleutosori dark brown; the uredo- 

 spores are 1-celled, round or more elongated and spiny; the stalk is detached; 

 the spores measure 23-38 x 20-26 ; teleutosori are elongated dark brown or 

 black being broadly elliptical and 2-celled, 30-52 x 16-24 ; the apex may be 

 thickened and somewhat pointed. These spores preserve their vitality for some 

 time; but are dormant through the winter. In the spring each cell may germin- 

 ate by producing a tube, known as the promycelium, which bears lateral bodies 



