Remarkable heterophylly is shown in this genus within the same species. Aristeguieta (Act. Ci. Venez. 3(2): 64-65. fig. 1-4. 1952) made observations of this phenomenon on Roupala montana Aubl. in the vicinity of El Junko, Distrito Federal, Venezuela. The same unusual heterophylly is displayed by R. suaveolens Kl., a species of the Guayana Highland. Various gradations in leaf division were encountered among the collections indicated above, all collected from the gallery forest along the Río Canaracuni at the base of the Meseta de Jaua at 400 meters altitude.
In Steyermark 97816 the adult leaves of the flowering tree are all simple, but vary from subentire to coarsely dentate along the basal margins to no. 97831 with adult leaves from flowering twigs all regularly pinnate with three pairs of entire leaflets. These two trees (no. 97816 and 97831) were growing next to each other. The lower twigs of 97816 produce pinnate leaves (Steyermark 97833) but vary on those farther up the twig to variously cleft, and some twigs show every transition from pinnately compound to simple leaves varying in only four leaves in a distance of less than 2 dm along the twig.
Similar variation is shown in a collection of R. suaveolens by Steyermark & Gibson 95738 (sapling leaves) and 95739 (adult leaves) from the Río Bonita (Caura River drainage) of Estado Bolívar, except that in this instance the sapling leaves are all pinnately compound, whereas those of the adult flowering twigs are all simple. Not so, however, in 97816, 97831, and 97833 from the Río Canaracuni, in which all transitions are found on the same tree and vary from flowering specimens with adult simple leaves to flowering specimens with adult compound leaves.
It is to be noted here that the Steyermark collections of 97816 show unusually coarsely dentate lower margins of the leaves, a character not mentioned by Sleumer for R. suaveolens, and the inflorescences of Steyermark 97816 and 97831 are twice as long as the length indicated by Sleumer for R. suaveolens. Sleumer’s description for R. suaveolens gives the leaf bases as broadly cuneate, but in Cardona 1804, cited by Sleumer under R. suaveolens, the leaf bases are broadly truncate or obtuse. It should also be pointed out here that the distinctions given by Sleumer in his key to differentiate R. suaveolens from R. schomburgkii do not hold true in a number of instances. Roupala schomburgkii is keyed out as having slightly cordate or subrounded (rarely broadly cuneate) leaf bases and with petioles 1-1.5 cm long, but in Cardona 1242, cited by Sleumer under R. schomburgkii, the leaf bases are quite cuneate and the petioles are longer.