1963] 



BOTANY OF THE GUAYANA HIGHLANDS PART V 



221 



New York Botanical Garden. It is fitting that the name of such a spectacularly 

 handsome shrub be associated with that of Maguire, who, by his numerous ex- 

 peditions into the remote hinterlands of southern Venezuela, has succeeded in 

 making available the mass of remarkable plant material existing there. The 

 present genus is restricted to the table-mountains (tepuis) of Venezuela which 

 Maguire has explored since 1944. 



This genus is a member of the tribe Rondeletieae and is related by its 

 loculicidally dehiscent capsules to the genera Ucriana Spreng., Phitopis Hook, f., 

 Macbrideinia Standi., and Sipanea Aubl. The latter is a genus of herbaceous 

 plants with short corollas resembling those of true Chalepophyllum. In the 

 arboreal genus Macbrideinia, known from Peru, the stipules are large and 

 caducous, the inflorescence is terminal and cymose-corymbose, the triangular 

 calyx-lobes are deciduous, and the anthers are exserted. In the genera Ucriana 

 and Phitopis, both of which are trees or shrubs, the deciduous stipules imme- 

 diately distinguish them from Maguireothamnus. They are further distinguished 

 by several other characters: in Ucriana the tube of the corolla is curved and the 

 valves of the capsule are spirally twisted to the base, whereas in Phitopis the 

 corolla is rather short and scarcely surpasses the unequally 2-3-lobed calyx. 



The genus Maguireothamnus, as thus constituted, is a closely-knit, distinct 

 one, with no closely related genera, geographically isolated on the slopes and 

 summits of the table-mountains of southern Venezuela. The species range from 

 Cerro Duida, Cerro Huachamacari, and Cerro Sipapo (Paraque) on the west to 

 Ptari-tepui, Roraima, and Serra do Sol on the east, its eastern limits on Roraima 

 extending to the British Guiana border and on Serra do Sol extending to the 

 Brazilian frontier. 



When N. E. Brown (Trans. Linn. Soc. Bot. II. 6: 33. pi. 5, figs. 10-17. 1901) 

 described Chalepopln/ll um speciosum, based on collections by Mc Connell & 

 Quelch (100, 305, 653) from the summit of Mount Roraima in Venezuela, he 

 assumed that his new species was congeneric with the Chalepophylliim guianense 

 Hook. f. described in 1873. Although the C. speciosum N. E. Brown with its large 

 showy corollas was an entirely different appearing plant from the small-flowered 

 C. (iuianense Hook, f., later botanists placed additional species of the large corolla 

 type under Chalepophyllum. Thus, Standley (Field Mus. Bot, Ser. 7: 379-381. 

 1931) described C. latifolium and C. tatei, based on the Duida collections of Tate, 

 and Gleason (Brittonia 3: 192. 1939) described C. coriaceum from collections of 

 Tate from the Auyan-tepui expedition. However, although Standley was certain 

 that his C. tatei was congeneric with the other large-flowered C. speciosum N. E. 

 Br., he was in doubt as to its congeneric status with C. guianense, stating (loc. cit. 

 p. 381) " There is no doubt that C. tatei is congeneric with C. speciosum, but 

 there is considerable doubt in the writer's mind regarding their relationship to 

 C. guyanense. Their status cannot be resolved, however, without access to mate- 

 rial of C. guyanense, and perhaps to better material than is afforded by the 

 type specimens. ' ' 



As a result of later expeditions by the present author and by Bassett Maguire 

 and his colleagues, a large amount of material of this Chalepophyllum group has 

 become available for study. Good fruiting material is amply represented in these 

 collections. They show, without doubt, that the plants consecutively described as 

 Chalepophyllum speciosum, C. latifolium, C. tatei, and C. coriaceum, all possess 

 loculicidally dehiscent capsules. This is quite in contrast to the very definitely 

 septicidally dehiscent capsules of the originally described Chalepophyllum, C. 

 guianense Hook, f . from British Guiana, type species of the genus. 



