PITTIER— PLANTS FROM COLOMBIA AND CENTRAL AMERICA. 109 



pollinia long pear-shaped, about 1.15 mm. long, subhorizontal. Stigma pentagonal, 

 slightly concave. 



Follicles not known. 



Costa Rica: Covering the trunks of fallen trees at Chirrip6 Farm, Zent Plains, on 

 the eastern coast, Pittier, flowers, February, 1900 (Instituto fis.-geog. Costa Rica 

 no. 16040; U. S. National Herbarium no. 573016, type). 



This Costa Rican species of Exolobus is the first representative of this genus, which 

 is mostly Brazilian, signalized in Central America. It is probable, however, that the 

 monotypic genus Trichostelma, founded by Baillon " on a Mexican species, must also 

 be referred to this genus, the only apparent difference being in the two lobules that 

 mark the center of the stigmatic surface. Our species comes near E. patens (Decaisne) 

 Fourn., from which it differs principally by the 4 glandules at the base of the leaf 

 blade, by the form of the sepals, and by the characteristic white margin of the petals. 



THE TRUE PLACE OF SOME SUPPOSED ENSLENIAE FROM MEXICO 

 AND CENTRAL AMERICA. 



Under the name of Enslenia? ligulata, Bentham 6 described a plant 

 collected by Hartweg at Aguascalientes, Central Mexico. As indi- 

 cated by the ? sign, the author was doubtful as to whether the use 

 of the generic name Enslenia was justified. Later, other specimens 

 from the same country and from Central America have been assigned 

 to the same species, and the interrogation mark has disappeared 

 without any indication of the dubious question ever having been 

 settled. The discovery by Dr. Renson of a new Roulinia led me to 

 take up the case, with the conclusion that Enslenia? ligulata Benth., 

 as well as several of the specimens collected later in Middle America 

 and found under the Enslenia cover in the U. S. National Herbarium, 

 must be transferred to the said genus Roulinia. 



The genus Enslenia was established by Nuttall, 6 ' who gives as its 

 nearest relatives Cynanchum and Asclepias. The type species is 

 E. albida, collected "near Shepherdstown, on the gravelly banks of the 

 Potomac, Virginia." Very good drawings of the characteristic fea- 

 tures of this species have been given by Karsten, d together with those 

 of his Enslenia volubilis. 



The closely related genus Roulinia, on the other hand, was named 

 and described for the first time by Decaisne, in his monograph of the 

 Asclepiadeae. c 



Improved descriptions of both genera are found in Bentham and 

 Hooker's Genera Plantarum/ the comparison of which shows that 

 the real distinction between the two is very small, but none the less 

 so well marked that a confusion should not be possible. In Enslenia, 

 namely, the corolla is bell-shaped, with the lobes more or less conni- 

 vent; the scales of the corona are parted from the base — or, we should 



a Hist. PL 10: 136. 1891. <*F1. Columb. 2: pi. 162. 1862-69. 



b PI. Hartw. 290. 1848. 'In DC. Prodr. 8: 516. 1844. 



cGen. PI. 1: 164. 1818. /2: 757 and 762. 



