28 . 



comparison is instituted between specimens from widely separated 

 regions, or from strongly dissimilar hosts. This species of Earlea 

 possesses an aecium exactly comparable in appearance and habit 

 of growth with that of the species of Pliragniidiiim under discus- 

 sion ; and in other ways a near relationship is evident. 



The fixity of characters in Earlea and the high variability in 

 Plivagmidmni as shown in American rose rusts present an inter- 

 esting contrast. Regarding the latter it may be safely asserted 

 that each species of Phragniidiinn has attained a degree of ortho- 

 genetic development and a diversity of characters corresponding 

 to those of the hosts on which it occurs, always, however, with 

 a certain lag due to the inhibiting nature of parasitism. 

 Purdue University, 



Lafayette, Indiana. 



THE PERENNATION OF THE CLOVER DODDER, 

 CUSCUTA EPITHYMUM MURR * 



By F. C. Stewart and G. T. French 



In almost all botanical writings the numerous species of 

 Cttsaita are all classed as annuals. It appears to be the prevail- 

 ing opinion that none of the dodders survive the winter in the 

 thread form and that, in order to perpetuate themselves, they 

 must start anew every j/ear from seeds. Yet, so long ago as 

 1868 Dr. Julius Kiihn made the announcement,! based on his 

 own observations, that clover dodder, Ciisciita Trifolii (= C. 

 Epitliyimuii), lives over winter on clover and alfalfa plants in 

 Germany. Also, Sorauer, in the second edition of his well-known 

 Handbuch der Pflanzenkrankheiten, published in 1886, states that 

 clover dodder is not annual but perennial, and that on perennial 

 plants it perpetuates itself more often by the further growth of 

 the previous year's dodder plants than by the germination of 

 new seeds. On the other hand, Frank, % ten years later, makes 

 an equally positive statement that the dodders are all annual 

 plants that start anew every year from seed. In 1900 Kiihn 



* Read before Section G of the American Association for the Advancement of 

 Science, Baltimore Meeting, December 31, 1908. 



■(" Ztschr. landw. Centralvereins der Provinz Sachsen 25 : 238. 

 X Die Kranlvheiten der Pflanzen, Zweite Aufl. 2 : 523. 



