340 UREDINEAE. 



living host. The latter, however, germinate only on dsath of the 

 host and after a resting-period {Eu-piiccinia, Schroeter). 



(a) Auteupuccinia : all forms of spore are present on the same 

 host-plant. 



Puccinia helianthi. Schwein. Sunflower-rust. This danger- 

 ous enemy of Helianthus was first observed in South Carolina 

 and Pennsylvania, U.S. America. In Europe it appeared first 

 to a serious extent in Eussia, where the sunflower is cultivated 

 on a large scale ; now it has a very general distribution. In 

 America it attacks both sunflower {H. annuus) and Jerusalem 

 artichoke (H. tuberosus), but its presence on the latter is as 

 yet doubtful in Europe. The mycelium appears first in the 

 lower parts of the plant and thence extends upwards ; its 

 presence is indicated by large brown leaf-spots, on which the 

 uredo-patches arise about the end of June. The teleutospores 

 make their appearance in autumn ; the aecidia and pycnidia in 

 spring (Aee. helianthi Wor.). Combative measures consist in 

 burning, or otherwise destroying, all sunflower debris in autumn. 



P. cirsii Schroet. On Carduus lanceolata. (Britain.) 



P. prenanthis (Pers.). On Pre^nxintlus, Lactuca, and Mulge- 

 dium. (Britain and U.S. America.) 



P. lampsanae (Schultz). On LampsaruL (Britain.) 



P. montana Fuck. On Centaurea. 



P. violae (Sebum.). (Britain and U.S. America.) The Violet- 

 rust. This parasite appears on both wild and cultivated species 

 of Viola, and frequently causes much damage. Malformation 

 and stunting of the host may accompany the formation of 

 aecidia. Fentzling investigated the swollen outgrowths produced 

 on the lower surface of the violet leaves, and found an increase 

 in all forms of the leaf-parenchyma ; the spongy parenchyma 

 included more cells, while both spongy and palisade parenchyma 

 consisted of rounder cells more closely packed together than in 

 the normal. 



P. aegra Grove. On Viola cornida, etc., and somewhat 

 different from the last species. (Britain.) 



P. mirabilissima Peck. On Berheris repens in America. 



P. silenes Schroet. On Silenc and Lychnis. (Britain.) 



P. pimpinellae (Strauss). On Pimpinella, Ohaerophyllum, 

 Anthriscus, Myrrhis, Athamantha, Ostericu.m, Angelica, Herachum, 

 Eryngium, etc. (Britain and U.S. America.) 



