Subshrub or perennial herb with woody base, 0.23-1 m tall, erect, 1-stemmed or branched from base with branches erect, lateral and rarely pseudo-dichotomous. Stems dull red- brown, 4(6)-lined and ancipitous when young, soon terete, cortex exfoliating irregularly; internodes 10-50 mm long, usually exceeding leaves. Leaves perfoliate, spreading or cyathiform; lamina 10-24(-30) x 12-34(-40) mm, ovate- deltoid to semicircular, margin revolute, incrassate, paler beneath, densely glaucous beneath or on both sides, coriaceous; apex obtuse-apiculate to rounded, bases completely connate or almost so; basal veins 1(3), midrib pinnately branched with3-4 main laterals, tertiary reticulum dense; laminar glands dense, slightly prominent beneath. Inflorescence c. 10-∞-flowered, rarely pseudo-dichotomous after first flower, otherwise dichasial/monochasial from upper node, very rarely with 1-2 lateral branches from the nodes below, the whole corymbiform; primary pedicels 1.5-5 mm long; bracts and bracteoles linear-lanceolate to subulate. Flowers 10-24 mm in diam., stellate; buds ovoid, acute. Sepals 6-8 x 2.5-3.5 mm, unequal, imbricate, ovate or rhombic to elliptic or spathulate, acuminate to acute; veins 5- 7, midrib or all slightly prominent; glands linear, punctiform in distal 2/3. Petals yellow to orange, 5-13 x 3-4 mm, 1.5-3 x sepals, oblong-oblanceolate to obovate; apiculus obsolete; glands linear, distally interrupted. Stamens 50-60 (-c. 100), obscurely 5-fascicled, shortly monadelphous, longest 3-5 mm long, 0.3-0.4 x petals. Ovary 2-2.5 x 1.5-2 mm, ovoid; styles 5(4), 2.5-3 mm long, c. 1.2 x ovary, spreading; stigma clavate to subcapitate. Capsule 5-6 x 4-5 mm, subglobose, shortly rostrate, almost equalling sepals. Seeds 0.7-1 mm long; testa ribbed-scalariform.
Pastures and dry, rocky places; 20-2021 m (Bolivia).
Brazil (São Paulo to Rio Grande do Sul), Uruguay, Argentina (Salta and Chaco south to San Luis and Buenos Aires), Paraguay, Bolivia (Chuquisaca, Tarija).
H. connatum resembles H. caprifoliatum in having the leaf pairs connate, but its leaves are coriaceous, not chartaceous, with a markedly incrassate margin (see Briquet (1919)) and nerves prominent beneath. The leaves are also relatively shorter and broader than in H. caprifoliatum, and the habit is less branched, often indeed with stems simple from the base. The plants nearest in form to H. caprifoliatum, with smaller flowers and leaves and branched stems, are from northern Argentina and Paraguay, whence there is a gradual trend towards basal branching with simple (annual?) stems, larger leaves, and larger flowers. The extreme in leaf size is apparently represented by the population from São Paulo that St.-Hilaire named H. chlorifolium; but the larger-leaved, larger-flowered form occurs throughout the range of the species and, in north-eastern Argentina and Paraguay, co- exists with the smaller-flowered form. It was no doubt this overlapping variation that prompted Briquet to describe his varieties; but there is no apparent gap in variation such as would allow the recognition of infraspecific taxa.
Briquet cites H. connatum Lam. as a synonym of his variety(H. connatum var. obscurum Briquet); therefore the selection of a Sellow specimen as lectotype by Rodriguez Jimenez cannot stand.
The selection of the Bolivian specimen as lectotype of H. connatum var. paraguariense Briquet by Rodriguez Jimenez (1973: 130) is not appropriate because: (i) Briquet chose the epithet paraguariense, and the other syntypes are all from Paraguay; (ii) Briquet described another part of Fiebrig 2361 as the type of his var. fiebrigii. I therefore propose the following specimen as substitute lectotype: Paraguay, Caaguazu, in campis in regione flumine Yhu, November 1905 (fl), Hassler 9686 (G!-lectotype; BM!, K!, P!, W!).
The herbarium symbols for H. connatum var. fiebrigii Briquet indicate where I have seen Fiebrig 2361. I have not noted which specimens are referable to var. paraguariense and which to var. fiebrigii.