370 



Sium cicutaefolnim Gmel., Wilmington, July 11, 1890, 1, A. 



Commons (1483). 

 On Cyperaceae: II, III. 



Scirpus americanus Pers., Lewes, Aug. 14, 1907, II, (1679, 



1689), June 6, 1908, (2091) ; Selbyville, Oct. 4, 1907, (1806). 

 Scirpus fluviatilis (Toir.) A. Gray, Collins Beach, Oct. 1, 1907, 



III, (1787). 

 In Europe P. Dietel (Hedwigia 29:149. 1890) was the first to 

 successfully connect this species with its aecial form. He showed by 

 cultures that aecia are produced on Sium latifolium and Hippurus vul- 

 garis. Plowright (Card. Chron. III. 7:682. 1890) added Glaux mari- 

 tima as an aecial host of this species. Bubak in Bohemia (Cent. Bakt. 

 9-:926. 1902) discovered a form which only infected Berula angustifolia. 

 Further cultures carried out by Klebahn (Jahr. Hamb. Wiss. Anst. 

 20:33. 1903) brought out new hosts and interesting biological relations. 

 . In America Arthur in 1906, 1907 and 1908 (Jour. Myc. 13:199. 

 1907; 14:17. 1908; Mycol. 1:237. 1909) showed that in America Cicuta 

 maculata was an aecial host. Fraser (Mycol. 4:178. 1912) confirmed 

 Arthur's work using telia on Scirpus campestris paludosus. 



The aecidium on Hydrocotyle Canbeyi is included here partly on 

 morphological grounds and partly on field observations. As noted above 

 the writer collected at Lewes, on Aug. 14, 1907, the aecidium on Hydro- 

 cotyle. The aecia were old and there was no evidence of uredinia or 

 telia of P. Hydrocotyles (with which form the aecidium has previously 

 been combined) on any of the affected leaves or on other plants in the 

 vicinity. Surrounding the plants, however, were plants of Scirpus 

 americanus abundantly affected with the uredinia of U. Scirpi. Obser- 

 vations and collections were again made in the same spot on June 6, 

 1908, when aecia were again found in abundance showing evidence of 

 having been mature for about two weeks. A few culms of Scirpus were 

 growing in such a position that the tips were hanging immediately 

 above the Hydrocotyle plants bearing the aecia. On the.se tips fresh 

 uredinial sori of U. Scirpi were present. No infection on Scirpus was 

 found elsewhere at that date though the plants were very abundant 

 over a wide area. 



