Monographs Details: Brunellia boliviana Britton ex Rusby
Authority: Cuatrecasas, José. 1985. Brunelliaceae (supplement). Fl. Neotrop. Monogr. 2: 28-103. (Published by NYBG Press)
Synonyms:Apopetalum pinnatum Pax, Brunellia pinnata (Pax) Cuatrec.
Discussion:Examination of more recently-available specimens of the type collections and of new collections from the Bolivian area, has shown that the characters given to distinguish Brunellia pinnata and its special subsection Apopetalae are not as consistent as formerly thought. This led to the idea that Apopetalum pinnatum Pax, should be considered a synonym of Brunellia boliviana Britton, and the subsection Apopetalae a synonym of subsection Bolivianae. Vegetatively, no noticeable differences are found between Brunellia boliviana and Apopetalum pinnatum. The latter was characterized by having a large number of stamens, which would have indicated triplostemonous flowers; this feature was considered important, also taking into account a major development of the flower base or thalamus. The additional specimens show considerable variety in the floral diagrams and floral formulae for every collection attributable to B. boliviana or B. pinnata, as follows:

Buchtien 746: 6S + 18a + 6C; 6S + 15a + 6C; 6S + 12a + 6C; 5S + 10a + 10C; 7S + 14a + 7C; 7S + 14a + 6C.

Buchtien 3108: 5S + 13a + 5C; 6S + 16a + 8C.

Buchtien 8952: 5S + 11A + 5c; 6S + 12A + 6c; 6S + 13A + 6c; 7S + 14A + 7c.

Bang 664:5S + 10a + 5C; 6S + 12a +6C.

Rusby 2577: 5S + 10A + 5c; 6S + 12A + 6c.

Cárdenas 5982:6S + 18A + 6c; 6S + 12A + 6c; 6S + 16A + 6c + 6S + 14A + 6c; 5S + 12A + 5c. Steinbach 5575:6S + 19a + 10C; 6S + 17a + 6C; 6S + 16a + 6C; 6S + 16a + 7C; 6S + 16a + 8C;

6S + 15a + 6C; 6S + 15a + 6C; 6S + 15a + 7C; 6S + 12a + 6C.

Davidson 4775: 6S + 14A + 6c; 6S + 13A + 6c; 6S + 12A + 6c; 6S + 13A + 5c; 5S + 10A + 5c. Beck 563: 6S + 12a + 6C; 6S + ?a + 6C; 6S + ?a + 7C.

Beck 1832: 6S + 13A + 6c; 7S + 15A + 7c; 7S + 14A + 7c; 7S + 14A + 8c.

These data indicate a dominance of the hexamerous flower with a hexamerous calyx. A heptamerous calyx is frequent and dominates in one collection (Beck 1832). Diplostemony is present but, in most flowers examined, the number of stamens is greater than twice the number of sepals. Triplostemony is found in some collections, e.g., 6S + 18a + 6C (Buchtien 746); 6S + 18A + 6c (Cárdenas 5982); in many cases the number of stamens comes very close to triplostemony (6S + 17A + 6C), or surpasses it, as in Steinbach 575: 6S + 19A + 10C. The number of carpels is also aberrant, being at least equal to the number of sepals (5, 6, 7), but frequently there are found one or two additional carpels. Given this wide oscillation in floral composition, it is not possible to maintain as distinct the two formerly separate "species."

It is appropriate to note that the instability of the flower of B. boliviana, as well as that of B. cuzcoensis (Cuatrecasas, 1970, p. 144) indicate that they may represent the oldest or ancestral type of Brunellia flower, from which the other living species are derived. Probably, we are seeing a trend to reduction in the evolution of the genus, towards a stable isomeric or diplostemonous flower, a feature already found in the majority of species.

With respect to vegetative characters it is still necessary to obtain more samples of leafy branches and terminal shoots to be able to completely understand the type of branching, position of leaves, stipules, stipels and indumentum.

The presently available specimens can be separated into two groups. One has completely glabrous leaves, coinciding with the type specimens of both B. boliviana Britton and B. pinnata (Pax) Cuatr. The other group shows a minute puberulence on the abaxial side of the leaves, the trichomes being very short, straight, pointed, hyaline, appressed or ascendent, as in the type of B. brittonii Rusby. Although at present this feature does not seem coordinated with any other visible character, it is constant within every collection, with no intermediate collections at hand; therefore, it seems reasonable to maintain the second form as var. brittonii (Rusby) Cuatrecasas.