Vol. 31, pp. 45-46 May 16, 1918 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



NOTES ON DISTRICT OF COLUMBIA JUNCACEAE. 

 BY FREDERICK V. COV1LLE AND SIDNEY F. BLAKE. 



In the preparation of the manuscript of the Juncaceae for the 

 District of Columbia Local Flora, it has been found necessary 

 to raise a variety of Juncus canadensis to specific rank, and to 

 employ new trinomials for two plants which appear to be variants 

 of Juncoides campestre. The reasons for these changes are dis- 

 cussed below. 



Juncus subcaudatus (Engelm.). 



.Inn nts canadensis var. subcaudatus Engelm. Trans. St. Louis Acad. Sci. 

 2 : 474. 1868. 



The distinctive characters of this form, hoth in habit and in seed, have 

 been recognized so long that it is surprising that the plant has not pre- 

 viously been granted the specific recognition it undoubtedly deserves. 

 J. subcaudatus differs from /. canadensis J. Gay in its more slender, often 

 lax or decumbent habit; in its looser inflorescence, with fewer-flowered 

 usually much less numerous heads on loosely spreading or sometimes 

 erect branches ; and particularly in its very different seeds. In J. cana- 

 densis the seeds are 1.3 to 1.5 mm. long, including the loose shining 

 whitish testa, which is provided with about 30 to 40 weak longitudinal 

 ribs only very obscurely, if at all, reticulate, and is prolonged at each end 

 into appendages or "tails " which are two-thirds or quite as long as the 

 body of the seed. In J. subcaudatus the seed, including the testa, is 0.7 

 to 0.9 mm. long, and the testa, produced at the ends into appendages 

 only one-third as long as the seed body or less, tightly encloses the dis- 

 tinctly plumper seed and is provided with about 20 to 25 strong longitudi- 

 nal ribs connected by distinct crossbars so that its surface appears areolate. 



In its seed characters ./. subcaudatus makes some approach to </". brevi- 

 caudatus (Engelm.) Fernald. The latter, however, has a strict contracted 

 inflorescence of few-flowered heads, and the capsule conspicuously exceeds 

 the perianth. 



Material of J. subcaudatus is in the National Herbarium from Pennsyl- 



14— Pkoc. Biol. Soc. Wash., Vol. 31, 1918. (4">) 



