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The Phyllodes of Oxypolis filiformis, a Swamp Xerophyte * 
By Rosina J. RENNERT 
A large number of species of higher plants which live in ponds, 
marshes and other extremely moist habitats present structural 
characters of a xerophytic nature which have been most difficult 
of interpretation. A special study of the phyllodes of Oxyfolis 
Jiliformis + was undertaken by the author in the hope that some 
additional light might be thrown on the subject. This work was 
carried on in the New York Botanical Garden under the direction 
of Dr. D. T. MacDougal, to whom I am indebted for valuable 
advice and fruitful suggestions. 
Oxypolis filiformis is an umbellifer which grows in swamps and 
along the borders of ponds in the southeastern United States, as 
far north as Delaware. The leaves exhibit curious modifications 
by which they depart widely from the uniformly broad or widely 
dissected umbelliferous type, being reduced to stiff grayish-green 
awl-shaped phyllodes, which have a structure as if made up of a 
number of sections of varying lengths, the joints being distinctly 
noticeable and marking the position of peculiar septa in the interior 
tissues. This habit of the leaves gives the plant a rush-like ap- 
pearance, an effect which is heightened by the small size of the 
cauline, and the strong development of the basal phyllodes. The 
entire phyllode is flattened along one side. A minute pit is to be 
observed externally to every septum, occurring in the middle ot 
the slightly flattened surface. 
Briquet { has given a detailed account of the results of his ex- 
amination of this plant with respect to the anatomy of the phyl- 
lodes. He describes the epidermis as a single layer of cells with 
curved outer walls protected by a thickened outer membrane and 
2 a eldes cuticle. The stomata were noted as either flush with the 
* Read before the Botanical Society of America, by invitation, at Pittsburg, Pa., 
July 1, 1902. 
+ Oxypouis FILIFORMIs ( Walt.) Britton. Tiedemannia teretifolia (Muhl.) DC. 
t Briquet, J. Etude de la feuille du Ziedmannia teretifolia DC. Bull. Herb 
Boiss. 5: 461-465. 1897. 
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