1 | Calyx lobes imbricate in bud |
1' | Calyx lobes valvate in bud |
2 | Stamens 10 or less, free |
2' | Stamens more than 15 |
3 | Sterile or non-functional male flowers at base of inflorescence, the sterile flowers with long staminodes |
3' | Sterile flowers without staminodes |
4 | Short-shoots terminated by spines or composed of many persistent fused stipules and (sometimes) bracts |
4' | Short-shoots without terminal spines |
5 | Stipules subulate. Fruits subsessile, linear, with oblique or longitudinal seeds |
5' | Stipules ovate to lanceolate, striately veined. Fruits stipitate, narrowly to broadly oblong, seeds more or less transverse |
6 | Shrubs or small trees armed with stipular spines or scattered spines, or with spine-tipped branches. Extrafloral nectaries generally present |
6' | Plants unarmed or armed with ± recurved prickles (then extrafloral nectaries absent) |
7 | Flowers in glomerules, with persistent spathulate or peltate bracts. Fruits papery to semicoriaceous, dehiscing down both sutures or opening along the margins only. Seeds compressed but not flat |
7' | Flowers in spikes or, if in glomerules, then fruits otherwise |
8 | Anther glands absent. Fruit valves separating, unwinged. |
8' | Anther glands present. Fruit valves ± winged, splitting at edges but not separating over the seed chambers |
9 | Leaflets alternate |
9' | Leaflets opposite |
10 | Plants unarmed |
10' | Plants armed with prickles on the internodes |
11 | Scandent shrubs or lianas. The distal pair of pinnae transformed into tendrils. Flowers in spikes |
11' | Trees or erect shrubs. Flowers in glomerules |
12 | Valves of fruit forming one-seeded segments at maturity leaving the sutures as an empty frame |
12' | Valves of fruit not forming one-seeded segments (India-Thailand, Indochina) |
13 | Fruit ± separating into individual segments to leave a persistent replum or if central part of pod separating as one piece the peduncle not prickly. |
13' | Valves of fruit separating as one unit from a ± persistent replum. Peduncle prickly |
14 | Filaments free or shortly united at the base only |
14' | Filaments united into a tube in the proximal part |
15 | Leaves unipinnate |
15' | Leaves bipinnate |
16 | Leaflets opposite or pinnae unifoliolate, proximal pair of leaflets rarely alternate, or leaflet unpaired |
16' | Leaflets alternate except perhaps the distal two; pinnae never unifoliolate |
17 | Stipules spinescent, or branches armed with spines |
17' | Stipules not spinescent, in one case recurved and persisting; plants unarmed. |
18 | Plants with ramous spines. Fruits falling apart in one-seeded segments. Seeds without aril |
18' | Plants with stipular spines. Fruits dehiscing along the sutures. Seeds with fleshy, funicular aril |
19 | Seeds with pleurogram |
19' | Seeds without pleurogram |
20 | Valves of fruit dehiscing elastically from the apex, recurving, margins thickened |
20' | Valves of fruit not dehiscing elastically from the apex, margins not or only slightly thickened |
21 | Flowers in glomerules or corymbs |
21' | Flowers in racemes or spikes |
22 | Flowers of the same inflorescence unit uniform |
22' | Flowers of the same inflorescence unit heteromorphic |
23 | Fruits woody, curved or curled, indehiscent. Seeds biserially arranged |
23' | Fruits membranous-chartaceous, straight, dehiscent. Seeds uniserially arranged |
24 | Fruit internally segmented. Seeds with an U-shaped areole. |
24' | Fruit usually not segmented inside; if segmented, then the seeds with a horseshoe-shaped areole |
25 | Endocarp forming a closed envelope around each seed; seeds strongly flattened, circular |
25' | Endocarp not forming a closed envelope around each seed; seeds ± flattened, ellipsoid |
26 | Fruits usually spirally contorted, reddish orange especially on the inner surface with contrasting bluish black seeds; if straight, then turgid with disc-like or bitruncate seeds |
26' | Fruits, where known, straight and flattened. Seeds strongly flattened, coin-like, with a narrow wing |
27 | Leaflets petiolulate. Pods curved into a circle or contorted, reddish inside, dehiscent |
27' | Leaflets sessile. Pods straight, not reddish inside, usually indehiscent or tardily dehiscent |