Monographs Details: Tabebuia insignis (Miq.) Sandwith
Authority: Maguire, Bassett. 1978. The botany of the Guayana Highland--part X. Mem. New York Bot. Gard. 29: 1-288.
Discussion:1. Tabebuia insignis (Miquel) Sandwith, Rec. Trav. Bot. Neerl. 34: 224. 1937.
Tabebuia fluviatilis Kl. in Schomb., Reise 3: 1085. 1848, non DC, 1845, nom nud.
T. triphylla Kl. in Schomb., Reise 3: 1085. 1848, non D C , 1845. nom nud.
Tecoma insignis Miq., Stirp. Surinam Sel. 122. 1850. Type. Surinam, Kappler 1697 (U).
Tabebuia roraimae Oliv., Trans. Linn. Soc. II. 2: 280, t 45. 1887. Type. Br. Guiana, Mt. Roraima, im Thurn 64 (K, US).
Gelseminum insigne (Miq.) Ktze., Rev. Gen. 2: 480. 1891.
Tecoma roraimae (Oliv.) K. Schum., Engler & Prantl, Nat. Pflanzenf. 4(3b): 238. 1894.
Tecoma dura Bur. ex K. Schum., Engler & Prantl, Nat. Pflanzenf. 4(3b): 238. 1894. Type. Br. Guiana, Schomburgk 658 (K).
Tecoma leucoxylon (L.) Mart, ex DC. var salpingophora Bur. & K. Schum., Mart. Fl. Bras. 8(2): 342. 1897. Type. Venezuela, Amazonas, Spruce 3374 (K).
Tecoma albiflora Ducke, Arch. Jard. Bot. Rio de Janeiro 4: 175. 1925. Type. Brazil, Rio de Janeiro, Ducke sn (RB 18173) (K, RB, U).
Bignonia dura Kl. ex R. Knuth, Fedde Rep. Beihefte 43: 638. 1927. nom nud.
Tabebuia dura (Bur. & K. Schum.) Sprague & Sandw., Kew Bull. 1932: 21. 1932.
Handroanthus durus (Bur. & K. Schum.) Mattos, Loefgrenia 50: 4. 1970.
In maintaining Tabebuia dura and T. roraimae as species, Sandwith (1957a) noted that they are probably habitat forms or varieties of J. insignis, and I agree. The only differences between T. dura and T. insignis are the former's narrower, usually 7-foliolate, leaflets and slightly longer (usually 2 cm long) calyx. The type of T. dura at Kew is actually closer to typical T. insignis than to most of the collections identified as T. dura; its leaves are mostly 5-foliolate but some are 3-foliolate and only one is 6-foholate. The two sheets of this collection include both leaves which are elliptic and acute to almost obtuse and leaves which are very narrowly elliptic or lanceolate-elliptic and sharply acute to acuminate. The queried comment "Mixture?" has been pencilled next to the former elements by Sandwith with a later note ''not necessarily." Acceptance of both forms of the type collection as belonging to the same species—a decision with which I agree—automatically reduces T. dura to the synonymy of T. insignis.
Typical Tabebuia roraimae differs from T. insignis (including T. dura) in its 3-foliolate leaves with small obtuse rigidly coriaceous leaflets densely whitishlepidote below. The undersurface of the leaflets has a characteristic roughsculpted surface with the areoles more densely lepidote than the somewhat prominulous and intricately reticulate ultimate venation. These leaf characters do not always vary together, however. Ule 8761 from the type locality on Mt. Roraima has leaflets both 5-foliolate and 3-foliolate and a few leaflets slightly apiculate. Maguire & Politi 27899 from Cerro Sipapo has much larger 3-5-foliolate leaves which are apiculate-acuminate but have a similar texture to T. roraimae. Tillett & Tillett 45301 (MO) has thick-coriaceous round-tipped leaflets with even the secondary veins hardly prominulous from the smooth undersurface. Several collections from the Gran Sabana approach the characteristic surface texture of T. roraimae but have acute to almost acuminate leaflets. In general, collections from over 1000 m have the typical thick-coriaceous texture and finely and intricately sculptured leaf undersurface of J. roraimae, while those from below 1000 meters lack it; the intermediate altitude collections tend to be somewhat intermediate, however, and the differences, though somedmes marked, appear too inconsistent for even varietal distinction.