Vascular Plant Herbarium

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NOTES ON THE PSIDIUM GRANDIFOLIUM COMPLEX

A revision of this complex is found in Sida 21(3): 1335-1354 (2005). At this site you can find a key to the taxa, images of the taxa, and lists of exsiccatae. The complex is considered to consist of just two species, P. grandifolium and P. australe, the latter with three varieties.

How is Psidium distinguished? Psidium is distinguished from other genera by a combination of floral and seed characters discussed in Landrum and Sharp [Landrum, L. R. and W. P. Sharp. 1989. Seed coat characters of some American Myrtinae (Myrtaceae): Psidium and related genera. Systematic Botany 14(3): 370-376], namely, flowers 5-merous with multiovulate locules; placenta often peltate; seed coat rough or dull, not lustrous, covered with a pulpy layer when wet; hard portion of seed coat (5--)8--30 cells thick at narrowest point, the cells thick-walled, elongate, overlapping.

How is the Psidium grandifolium complex distinguished? The species have in common 1) a shrubby habit, ability to resprout from underground stems after fires; 2) young twigs that are usually square or 4-winged in cross-section; 3) leaf venation that is usually eucamptodromous proximally to brochidodromous distally with a poorly defined marginal vein; 4) a placenta that protrudes little and that is completely hidden by numerous ovules at anthesis; and 5) seeds that are relatively smooth (but not lustrous) and rounded. A similar group, the P. salutare complex (Landrum 2003), has the same habit and ability to resprout vigorously after fires, and smooth, round seeds, but the twigs are not winged, the venation is entirely brochidodromous and the peltate placenta is clearly visible in dissections with one or two rows of ovules on each side.

List of exsiccatae for Psidium grandifolium

List of exsiccatae for Psidium australe

Key to the species of the Psidium grandifolium complex:

1.Calyx of flower bud with lobes about triangular, 2-5 mm long, about as long as wide.
2. Leaves thinly pubescent to glabrous. .............................................P. missionum
2. Leaves densely tomentose below. ...............................................P. grandifolium


1. Calyx of flower bud nearly closed or the lobes truncate to broadly triangular, about 2 times wider than long.

3. Flower bud just before anthesis 6-15 mm long, densely lanate, the underlying surface of hypanthium hidden, the calyx usually nearly closed; leaves whitish lanate below, generally at least some widest near the middle. ...................................................................................... Psidium grandifolium
3. Flower bud just before anthesis 5-10 mm long, moderately covered with hairs to glabrous, the underlying surface of hypanthium visible through hairs (if present), the calyx open or nearly closed; leaves glabrous to densely short pubescent below, generally widest above the middle. ..................................................................................................... P. australe


Key to the varieties of Psidium australe:

1. Leaves densely covered with hairs beneath, the underlying leaf surface (except for larger veins) hidden by hairs. ........................................................P. australe var. argenteum

1. Leaves sparsely covered with hairs to glabrous beneath

2. Leaves often 3 or more times as long as wide, lustrous above; peduncles usually more than 2 cm long, usually 3-flowered; calyx usually nearly closed in young bud; seeds up to ca. 10. ................................................. P. australe var. suffruticosum

2. Leaves usually less than 3 times as long as wide, usually dull above; peduncles commonly all less than 2 cm long, usually 1-flowered; calyx usually open in young bud; seeds up to ca. 50. ....................................................P. australe var. australe