From Mori et al. (in review)

Grias clade (Mori, 1979a)—species of Grias have a pachycaulous growth form, cylindrical trunks to the ground, thick stems, and very large leaves, which can reach two meters (Fig. 2E). Although there are species with four petals in a few other genera, Grias always has flowers with 4 petals, actinomorphic androecia (Fig. 2A), and a fleshy staminal tube that differs from the other genera by having a lower, narrower chamber that surrounds the ovary and an upper wider chamber that slants (Fig. 2B) or arches (Fig. 2G) outward. The staminal tube in Allantoma is also fleshy but it is the same diameter throughout its length. The stamens of Grias are always curved inward with filaments that are more-or-less angular (in cross section) and anthers that are shorter and have a more-developed connective than those of other neotropical Lecythidaceae. In addition, Grias flowers usually have four locules (Fig. 2C), although some have three (Fig. 2H) or more than four, with only a few, pendulous ovules at the apex of the locules and placentae that are not expanded (i.e., they are the same thickness throughout their length when viewed in a medial longitudinal section).  All species of Grias have fruits with a single seed and a very strongly ribbed endocarp; the ribs are called endocarp buttresses (Fig. 2C–D). The embryo is macropodial (i.e., it lacks cotyledons).