Difference between Acmella calva, A. oleracea and A. paniculata as per research gate link;
The following key can help differentiating species in India of species earlier treated under Spilanthes
1a. Heads with white ray florets, achenes 3-angled ……. Blainvillea acmella
1b. Heads discoid or with yellow ray florets, achenes flattened …….(2)
2a. Heads discoid ……(3)
2b. Heads radiate, ray florets very small, achenes ciliate, pappus of 2-3 bristles ………(7)
3a. Corolla white, greenish white or with purple tinge, 4-merous, pappus of 2-3 bristles …..Acmella radicans var. radicans
3b. Corolla pale yellow, yellow or orange yellow …(4)
4a. Pappus absent; stems decumbent, rooting at nodes; leaves ovate, ahenes 1.7-2.2 mm, glabrous, if sparsely hairy then hairs hooked ….Acmella calva
4b. Pappus of 2-3 bristles, achenes hairy, hairs straight, stems erect without nodal roots…..(5)
5a. Mature achenes with cork-like margin; surface tuberculate …….Acmella paniculata
5b. Mature achenes without cork-like margin; surface not tuberculate …..(6)
6a. Corolla (disc floret) 4-merous, phyllaries 5-6, uniseriate, heads 5.8-8 mm high, 4-6 mm diam.,receptacle 3-6 mm high ……Acmella uliginosa
6b. Corolla 5-merous, phyllaries 15-18, triseriate, heads 8-23 mm high, 6-17 mm diam., receptacle 6-21 mm high, leaves ovate-deltate ……Acmella oleracea
7a. Mature achenes with evident cork-like margin; disc corolla 5-merous; heads ovoid; leaves broadly ovate with rounded to cordate base; phyllaries 7-10, biseriate; heads 6-10 mm high, 6-9 mm in diam, receptacle 4-8 mm high ……Acmella ciliata
7b. Mature achenes without cork-like margin; leaf base cuneate ………(8)
8a.. Disc corolla 4-merous, heads cone-shaped; leaves elliptic to narrowly ovate, cuneate at base; phyllaries 5-6, heads 5.8-8 mm high, 4-6 mm diam. receptacle 3-6 mm high; achenes 1.2-1.8 mm long, ciliate with straight hairs; pappus of two unequal or subequal bristles, one up to 0.7 mm long second up to 0.5 mm long …..Acmella uliginosa
8b. Disc corolla 5-merous; phyllaries 8-11, biseriate; heads 7.5-11.5 mm high, 6-8.5 mm diam, receptacle 5-8.5 mm high; achenes ahenes 1.7-2.2 mm, glabrous, if sparsely hairy then hairs hooked; pappus absent ……Acmella calva
Fwd: completed insertion of images of identified Acmella species : 1 post by 1 author.
Pl. go through Acmella page with images of species (mainly done by Bhagyashri Ranade ji) in efloraofindia.
If you find any mis-identification, pl. let us know. If anybody can send images of other species of this genera (for incorporation in the website), if any, it will be really nice.
Also, if anybody is interested to take up the activity of inserting images on efloraofindia pages from efloraofindia posts, pl. let us know.