Monographs Details: Chamaecrista nictitans subsp. nictitans var. diffusa (DC.) H.S.Irwin & Barneby
Authors:Howard S. Irwin, Rupert C. Barneby
Authority: Irwin, Howard S. & Barneby, Rupert C. 1982. The American Cassiinae. A synoptical revision of Leguminosae tribe Cassieae subtrib Cassiinae in the New World. Mem. New York Bot. Gard. 35, part 2: 455-918.
Family:Caesalpiniaceae
Synonyms:Cassia diffusa DC., Chamaecrista diffusa (DC.) Britton, Cassia brachycarpa Urb., Cassia exunguis Urb., Chamaecrista exunguis (Urb.) Britton, Chamaecrista (L.) Britton chamaecrista
Description:Species Description - Heteromorphic in growth-habit, either erect and simple from a shallow annual root in maturity becoming branched distally, or diffusely to humifusely branched from a usually monocarpic but sometimes short-lived perennial root, the stems at anthesis (0.3-)0.5-6(-7) dm, puberulent with fine incurved hairs up to 0.2-0.7 mm and the stems distally with lf-stalks in addition often pilose with longer more widely spreading-ascending ones up to 0.7-1.7 mm, the lifts commonly puberulent beneath and glabrous above, sometimes glabrous on both faces, always at least minutely ciliolate, sometimes pilose-ciliate. Adult lvs either associated with fls or produced only beyond the early fls (in starveling or very young individuals sometimes absent) 1.5-6.5(-7) cm, early (rarely all) lvs shorter and simpler; petiole 2-5 mm; petiolar gland 1, circular, shallowly saucer-shaped or almost discoid, (0.15-)0.2-0.5(-0.6) mm diam, stipitate, the stipe either slenderly linear or stouter and gradually dilated upward, (0.2-)0.3-l mm tall, the whole longer than or as long as diam; lfts of early lvs and those of many lateral branchlets 5-8, of most adult lvs (7-)8-20(-22) pairs, linear or narrowly oblong, up to (3—)5—15(—18) x 1-2.6 mm. Pedicels 1-3, at anthesis 0.5-4(-4.5), in fruit (1.5-)2-6 mm; sepals up to (3.5-) 3.8-6(-6.2) mm; long abaxial petal and cucullus of about equal length, 3.7-6 (-6.2) mm, 0.8 mm shorter to 0.2(-0.5) mm longer than the longer sepals; stamens usually 10, 5 much smaller, 1 rarely staminodal or wanting, 3 larger with anthers up to (1.8-)2.1-4.2(-4.5) mm; ovary either strigulose or pilosulous; style 0.9-1.6 mm, not or scarcely dilated, at apex 0.2—0.3 mm diam. Pod (14-) 17-37 x 2.4-3.7(-4) mm, the fuscous, reddish-castaneous, or nigrescent valves either incurved-puberulent or finely spreading-pilosulous; seeds 1.9-2.5 mm, the testa overall light brown, or this fuscous-pitted, or fuscous overall, dull.—Collections: 95.

Distribution and Ecology - Rocky and sandy seashores, savannas, streamside sands and gravels, sometimes on dunes or in pine woods, becoming weedy in waste places, fallow fields, gardens, and in packed soil of paths and highway margins, mostly below 300 but in Hispaniola up to 1200 and in n. Venezuela to 1600 m, locally common but discontinuously dispersed around the e. and centr. Caribbean basin, from Jamaica through e. Cuba (Oriente), Hispaniola, Puerto Rico, Virgin Is. (St. Thomas, St. John, St. Croix), Leeward Is. (St. Barthélemy, St. Kitts), Windward Is. (Guadeloupe, St. Vincent, Grenada) to the Lesser Antilles (Aruba, Curaçao, Bonaire) and n. Venezuela (Isla Margarita, seaward slopes of Miranda, Lara and Distrito Federal, and Pemsola de Paraguaná in Falcón); extending feebly n. from Haiti to the Bahamas (South Caicos and New Providence), there sympatric with var. aspera; apparently disjunct near 250 m in the middle Orinoco (Atabapo) valley in n.-e. Vaupés, Colombia.—Fl. primarily X-III, but in weedy circumstances or granted moist subsoil intermittently through the year.

Discussion:

Our concept of var. diffusa is nearly equivalent to Britton’s Chamaecrista chamaecrista, and includes a diversity of growth- and pubescence forms collectively characterized by small stipitate petiolar glands, ciliolate leaflets, a tiny decandrous flower with two larger abaxial petals which are subequal in length and shorter to barely longer than the sepals, and a linear style. It is of interest to note in passing that Britton in this case permitted within one species both erect annual and prostrate more enduring life-forms, doubtless because he had himself found them growing together on the islands of St. Kitts and Curaçao, as they have been encountered elsewhere by others (see the suite of specimens, NY, US, collected by Leonard on Ile de la Tortue, Haiti, nos. 11605, 11708 erect, nos. 13339, 14066 prostrate).

As characterized herein, var. diffusa differs from the sympatric var. glabrata, the dwarfer forms of which are virtually identical in habit, in the smaller flower, the tack-shaped rather than sessile or obconic petiolar gland, and the generally narrower pod; from mostly allopatric vars. aspera and nictitans in the ciliolate leaflets and usually perfect decandry, from the first further in the more dilated gland and from the latter, but less consistently than from marginally sympatric var. aspera, in having the two carinal petals of subequal length. The sometimes habitally inseparable var. jaliscensis differs principally only in the dilated style, while distantly allopatric var. mensalis, which has the same style, differs in the more reduced androecium and more unequal carinal petals.

The var. diffusa was described first by Breynius from Curaçao in 1678, and his figure, excellent except for the fancifully misrepresented androecium, was cited by Linnaeus in the protologue of Cassia chamaecrista. Our reasons for rejecting this element of the mixed C. chamaecrista as alone typical, the choice of Pennell (1917) and all subsequent students of the group, were set out under C. chamaecrista Linn. emend. Benth. in an earlier paper (Irwin & Barneby 1976 p. 437-439).

Distribution:West Indies| Venezuela South America| Jamaica South America| Cuba South America| West Indies| Oriente Cuba South America| Puerto Rico South America| Virgin Islands South America| Saint Thomas Virgin Islands of the United States South America| Saint John Virgin Islands of the United States South America| Saint Croix Virgin Islands of the United States South America| Saint Barthélemy South America| Saint Kitts Saint Kitts and Nevis South America| Guadeloupe South America| Saint Vincent and the Grenadines South America| Grenada South America| Aruba South America| Curaçao South America| Bonaire South America| Venezuela South America| Miranda Venezuela South America| Lara Venezuela South America| Distrito Federal Venezuela South America| Falcón Venezuela South America| Haiti South America| Bahamas South America| Turks and Caicos Islands South America| New Providence Bahamas South America| Vaupés Colombia South America| Colombia South America|