| | 1. Calyx radial, sepals ± equal, > nutlets; nutlet margins ± entire, not dentate; lower cauline leaves opposite, fused at base (sect. Gruvelia) |
| |
| | 2. Sepal tip with hooked bristles; stems and sepals with appressed, short hairs; nutlet margins not membranous-winged; pedicel in fruit 1–2.3 mm; nutlets 4-sided, not paired |
| P. pusilla |
| | 2' Sepal tip with straight bristles; stems and especially sepals with appressed, short and several spreading, long, stiff hairs (including bristles); nutlet margin generally widely membranous-winged; pedicel in fruit ± 0.5 mm; nutlets ± obovate to ± round, paired |
| P. setosa |
| | 1' Calyx bilateral, upper 2 sepals > others, all < nutlets; nutlet margins entire to generally dentate; lower cauline leaves mostly alternate, free (sect. Pectocarya) |
| |
| | 3. Basal flowers cleistogamous; basal nutlet margins less ornamented than cauline |
| |
| | 4. Pedicel in fruit partly fused to 1 nutlet; cauline nutlets generally curved; lower 3 sepals unequal |
| P. heterocarpa |
| | 4' Pedicel in fruit free from nutlets; cauline nutlets generally straight; lower 3 sepals ± equal |
| P. peninsularis |
| | 3' Basal flowers not cleistogamous; basal, cauline nutlet margins similarly ornamented |
| |
| | 5. Nutlet margins ± entire, not or barely dentate |
| P. penicillata |
| | 5' Nutlet margins dentate |
| |
| | 6.Nutlet strongly recurved to coiled, linear; nutlet margin teeth distinct ± to base |
| P. recurvata |
| | 6' Nutlet straight to moderately recurved, ± oblanceolate; nutlet margin teeth distinct ± to or fused at base |
| |
| | 7. Stems prostrate to decumbent; nutlet margin teeth generally narrower at base than length, distinct ± to base; nutlets straight or slightly recurved at tip |
| P. linearis subsp. ferocula |
| | 7' Stems ascending to erect; nutlet margin teeth ± as wide at base as length, fused at base; nutlets slightly to moderately recurved ± throughout |
| P. platycarpa
|