CONTRIBUTIONS FROM THE GRAY HERBARIUM OF 

 HARVARD UNIVERSITY, NEW SERIES, No. XV. 



By M. L. Fernald. 



Presented by B. L. Robinson, March 8, 1899. Received March 15, 1899. 



I. — ELEOCHARIS OVATA AND ITS AMERICAN ALLIES. 



In attempting to place satisfactorily a number of strikingly different 

 American plants, which, according to the standard works upon that 

 group, must all be called Eleocharis ovata, a detailed study of the achenes 

 has shown that our present conception of the species — especially in 

 America — is remarkably indefinite. The commonest American plant 

 passing as Eleocharis ovata is an annnal species with many erect or 

 ascending comparatively stout culms from 1 to 5 dm. high, capped by 

 thick globose-ovoid or ovate-oblong obtuse densely flowered brown heads, 

 3 to 13 mm. long. The closely a^ipressed ascending obovate-oblong or 

 suborbicular scales are blunt, with scarious margins. The tubercle, 

 usually as broad as the cuneate-obovate achene, is depressed, somewhat 

 resembling in outline a high-crowned tam-o'-shanter cap; it is generally 

 one third as high as the body of the achene. This common American 

 plant (Figs. 1 to 7), now accepted as E. ovata, was described in 1 809 by 

 Willdenow as Scirpus obtnsus, and it was subsequently transferred by 

 Schultes to Eleocharis. For three fourths of a century the plant was 

 generally treated by Torrey, Gray, and other recognized authorities on 

 the group, as a distinct American species. In his monograph of the 

 Cyperacece, however, Burkeler reduced^ our common American Eleo- 

 charis {Heleocharis) ohtusa to the well known E. ovata. of central 

 Europe. This disposition of the plant was accepted by Mr. C. B. Clarke 

 in his study of the European species of Eleocharis,'^ and it has been 

 adopted by subsequent American students of the group, — Britton, Wat- 

 son, etc. Habitally the two plants are essentially alike, but a careful 

 examination of achenes from an abundance of American and European 

 specimens reveals certain differences which appear quite constant. The 



1 BGckeler, Linnaea, (1869-70), XXXVI. 463. 2 Jour. Bot., XXV. 268. 



