THE FUNGI WHICH CAUSE PLANT DISEASE 



373 



U. fabae (Pers.) De B.^^ This is an autcecious eu-type which 

 causes a rust of the broad bean, vetches, peas. 

 U. trifolii (Hed.) Lev.^i-^^s An autcecious eu-type. 



I. Mcia, m circular clusters, on pallid spots. Peridia shortly 

 cylindric, flattish, on the stems in elongated groups; edges whit- 

 ish, torn. Spores subglobose or irregular, finely verrucose, pale- 

 orange, 14-23 n in diameter. 



II. Uredinia pale-brown, rounded, scattered, surrounded by the 



Fig. 269. — Uromycea appen- 

 diculatus, teliospore ger- 

 minating. After Tulasne. 



Fio. 270. — Uredini- 

 osporc and telio- 

 spore of Uiomy- 

 ces trifolii. Af- 

 ter Cobb. 



torn epidermis. Spores round or ovate, with three or four equa- 

 torial germ pores, echinulate, brown, 20-26 x 18-20 /i. 



III. Telia small, rounded, almost black, long covered by the 

 epidermis. Spores globose, elliptical or subpyriform, with wart- 

 like incrassations on their summits, smooth, dark-brown, 22-30 x 

 15-20 fi. Pedicels long, deciduous. 



Cosmopolitan on white, crimson and alsike clovers. Stages 

 and I are most common on Trifolium repens, least common on 

 T. incamatum. Pycnia appear in early spring or even in winter. 

 Theaeciospores germinate readily in water and give infections which 

 give rise to urediniospores in about two weeks. Urediniospores 

 maj'^ be produced throughout the summer and may even survive 

 the winter. Teliospores are produced in the uredinia or in 

 separate sori late in the season. The teliospores by infection 



