Monographs Details: Declieuxia cacuminis var. decurrens J.H.Kirkbr.
Authority: Kirkbride, Joseph H., Jr. 1976. A revision of the genus Declieuxia (Rubiaceae). Mem. New York Bot. Gard. 28 (4): 1-87.
Description:Latin Diagnosis - A D. cacuminis var cacuminis stipulis 1-dentatis, decursivis, lobis calycinis 0.2-0.4 mm longis, corolla azurea, extus glabra, mericarpiis 1.5-2.1 x 0.8-1.1 mm, 0.2-0.4 mm crassis differt.
Discussion:25b. Declieuxia cacuminis var decurrens Kirkbride, var nov.
Types: Brazil, Minas Gerais, ca 8 km W of Grão Mogol, 950 m, 16 Feb 1969, Irwin, Reis dos Santos, Souza, Fonsêca, 23348 (holotype UB; isotypes F, G, K, NY, RB, UB, US); ca 15 km W of Grão Mogol, 950 m, 19 Feb 1969, Irwin, Reis dos Santos, Souza, Fonseca 23539 (paratypes BR, C, F, LE, LIL, NY, UB, US); Serra de Grão Mogol, Pagão, 1000 m, 12 Nov 1938, Markgraf 3479, Brade, Barreto 12079 (paratypes F, RB). Map 19.
Declieuxia cacuminis var decurrens is well set off from D. cacuminis var cacuminis by its decurrent stipules, white corolla with a glabrous exterior, and slightly smaller fruit. Its habit is more open, the longer internodes making the general appearance not ericoid. Also, the pubescence is much less dense, with the hairs on the mature fruit longer.
Declieuxia cacuminis and D. coerulea are more closely related to each other than either is to any other species of Declieuxia. D. coendea is most similar to D. cacuminis var cacuminis in habit, vegetative morphology, and ecological adaptions. They are both found at higher elevations, “above tree line,” in areas which are cool and often cloud-covered. A large part of the vegetation cover consists of Gramineae and shrubs of ericoid habit on a shallow zone of very black soil overlying sand.
On Pico do Itambé, I observed that there seemed to be 2 vegetative forms of D. cacuminis var cacuminis. Some of the plants tended to have longer internodes and stipules and larger leaves. One plant was encountered with branches displaying each type. The branches with enlarged structures more closely resemble D. cacuminis var decurrens. Some parts of the type collections of D. cacuminis var decurrens have larger leaves without a corresponding increase in size of the internodes or stipules. The herbarium specimens of D. coendea also seem to generally fall into 2 groups similar to those found in D. cacuminis var cacuminis. The distinction does not seem quite as strong but none the less is evident.
The differences between D. cacuminis and D. coerulea lie in inflorescence and floral structures. The inflorescences of D. coendea are smaller and closer to the basic cymose pattern with more groups of 3 flowers subtended by 2 bracts. The inflorescences of D. cacuminis are larger with a greater number of single flowers and pairs of flowers subtended by 2 bracts while very rarely exhibiting 3 flowers subtended by a pair of bracts.
The most striking differences between the 2 species are found in their flowers. Declieuxia cacuminis has 4 smaller calyx lobes and a solitary basal ovule attached by its funicule in each locule, while D. coendea has 2 larger calyx lobes and a basally attached placenta with 1 or occasionally 2 ovules in each locule. The presence of 2 calyx lobes and the placenta is encountered in no other species of Declieuxia except D. coerulea.