KEY TO THE SPECIES OF TILLANDSIOIDEAE BASED ON VEGETATIEVE CHARACTERS

1Plant caulescent, leaves evenly distributed along the stem; the blades not over 1.5 cm wide.
1'Plant acaulescent, leaves rosulate.
2Stem very slender, exposed for most part and branching at each node; plant up to 8 m long, growing pendent from trees in branching strands.
2'Stem (sub-) stout and hidden by the leaves.
3Plant short- to long-caulescent (the stem often longer than the leaves); leaf blades often secund and rigid, their bright yellow-green color not masked by the scales, stramineous when dry.
3'Plant short-caulescent; the leaves cinereously lepidote, or when glabrescent then the leaves thin (not at all rigid).
4Sheaths ample, convex, merging or contracted into the blade.
4'Sheaths inconspicuous, hidden and clasping the stem.
6Sheaths concolorous with the blade or pale-brown, not dull ferrugineous- lepidote; the lyaf blades thin, soon lustrous-green, or when cinereous then not over 12 cm long.
6'Sheaths brown or dull ferrugineous-lepidote; the leaf blades coriaceous, or when thin then densely appressed-lepidote, at least at the underside.
7Sheaths about as long as, and indistinctly merging into the blade; the leaf blades triangular-acute, yellowish-green.
7'Sheaths much shorter than the blade; the leaf blades long attenuately acute or filiform attenuate.
8Plant with a very small (to 14 cm) crateriform rosette; sheaths often purple-red at the inside; leaf blades densely appressed-lepidote throughout.
8'Plant with a dense subspreading rosette, 15-45 cm tall; leaves often red- striate at the base, densely and minutely lepidote, somewhat lustrous-green.
9Sheaths and leaf blades pale-green, chartaceous when dry; leaf blades not over 1.2 cm wide, sublinear, long filiform attenuate.
9'Leaves thin but not chartaceous, 1-2.5 cm wide, attenuately acute and pungent.
10Sheaths not dull ferrugineous-lepidote; the leaf blades coriaceous and rigid
10'Sheaths often dull ferrugineous- or pale-brown appressed-lepidote; the leaf blades not rigid.
11Sheaths distinct; the leaves arching or erect, not transversally white-banded
11'Sheaths ample, concolorous with the blade and indistinct; the leaves mostly twisting in one direction, the outer ones much reduced and sheathlike, nearly always transversally white-banded (caused by subspreading scales).
12Sheaths minutely brown-lepidote; the leaf blades 2-3 cm wide, arching or erect (often involute-subulate when dry), cinereous-lepidote throughout.
12'Sheaths concolorous with the blade or nearly so, densely appressed-lepidote; leaf blades mostly over 3 cm wide, sparsely lepidote.
13Sheaths appearing white-pruinose toward the apex, caused by subappressed scales; leaf blades subcoriaceous, 30-50 cm long, filiform-attenuate, pale- yellowish when dry.
13'Sheaths not pruinose and the blade often much smaller.
14Plant with a small (ca. 25 cm) crateriform rosette, sheaths very dark ferrugineous at both sides; leaf blades (sub-)coriaceous often second (sometimes invo1ute-subulate and rigid when dry), cinereous-lepidote, filiform attenuate.
14'Plant with a larger rosette, or when small, the leaf blades not coriaceous or secund, sheaths pale ferrugineous-lepidote at the outside, at least below.
15Sheaths large, about as long as the blade, densely pale-brown or ferrugineously appressed-lepidote, deep purple-brown at the inside; the leaf blades 4.5-5 cm wide, triangular-acute or slightly acuminate, cinereous at the outside, less lepidote at the inside.
15'Sheaths much shorter than the blade, or the blade not over 4 cm wide and densely cinereous-lepidote on both sides.
16Sheaths dark ferrugineous-lepidote toward the apex, and more pale-brown appressed-lepidote toward the base; leaf blades erect, densely cinereous at both sides, (triangular-)acute.
16'Sheaths brown appressed-lepidote for most part; leaf blades arching, cinereous-green and often soon less lepidote at the upperside, mostly filiform attenuate.
5Leaf blades somewhat fleshy, more or less rigid, to ca. 1.2 cm wide, often secund but not reflexed, very densely covered with subspreading scales, cinereous-green.
5'Leaf blades thin, the lower ones mostly reflexed, to ca. 1.5 cm wide, densely appressed-lepidote, rich-green.
17Plant with a pseudobulb or an utriculate rosette; the sheaths inflated and convergent at their apices.
17'Plant with a dense or open rosette; the sheaths divergent.
18Leaf blades fleshy (succulent) or rigid.
18'Leaf blades thin and often undulate at the base.
19Leaf blades very densely white or ferrugineously tomentose-lepidote, mask- ing the color of blades.
19'Leaf blades covered with appressed or subappressed scales.
20Sheaths largely inflated, orbicular, abruptly contracted into the blade, forming an ovoid pseudobulb.
20'Sheaths less inflated-convex, more ovate, merging into the blade, forming an elongate pseudobulb or a more utriculate rosette.
21Leaf blades fleshy, involute-subulate, covered with minute appressed scales, somewhat lustrous green (to purple-red).
21'Leaf blades coriaceous, not fleshy, sometimes involute when dry, densely cinereously lepidote throughout.
22Sheaths not over 3 cm wide; the leaf blades not over 2 cm wide, erect to strongly arching, evenly and densely covered with subappressed scales.
22'Sheaths and leaf blades often much wider, mostly strongly arching and twisting and irregularly covered with appressed and subappressed scales
23Sheaths ample, contracted into the blade; leaf blades 0.4-1 cm wide, often for most part undulate, long filiform attenuate, rich-green and often purple-red spotted.
23'Sheaths merging or slightly contracted into the blade; leaf blade 1-4.5 cm wide, only undulate at the base, subacute or rounded and acuminate.
24Leaf blades very narrowly triangular, evenly tapering from the base to the apex, or triangular-ovate-lanceolate, not over 50 cm long.
24'Leaf blades not evenly tapering from the base to the apex, linear (-lanceolate) or ligulate.
25Leaves uniformly pale- or rich-green, often white-cretaceous toward the base, and not over 45 cm long; sheaths about as long as the blades, but indistinctly merging into, and mostly concolorous with them, sometimes pale-brownish at the base.
25'Leaves never white-cretaceous; sheaths often distinct by shape or color
26Plant to ca. 25 cm tall; leaves broadly rounded and apiculate or appearing emarginate, often deep-green.
26'Plant to 45 cm tall, but often less than 35 cm; leaves triangular-acute or acuminate, often yellow-green.
27Leaf blades not over 25 cm long and not over 4.5 cm wide, often less than twice as long as the sheaths, mostly marked or spotted with purple-red or in great part purple-red colored.
27'Leaf blades often much larger or more than twice as long as the sheaths
28Sheaths for most part dark castaneous at the outside, appearing pruinose caused by a coat of white scales; leaf blades with a fine wavy pattern of darker-green or maroon lines (often lost when dry).
28'Sheaths not castaneous at the outside, and not appearing pruinose, leaf blades not with a wavy pattern.
29Plant with a compact cyathiform or crateriform rosette; sheaths concolorous with the blade or somewhat brownish at the outside, contracted into the blade; leaves often undulate and marked with red.
29'Plant with a subfunnelform or spreading rosette; sheaths not distinctly contracted into the blade; leaves not undulate.
30Leaf blades (thin-) coriaceous, triangular-acute to a short filiform tip, often slightly involute near the apex, then appearing acuminate
30'Leaf blades thin (chartaceous when dry).
31Sheaths concolorous with the blade or pale-brown at the inside, sometimes longitudinally red-striate.
31'Sheaths dark purple at the inside and often partly so at the outside; the leaf mostly broadly rounded and apiculate, sometimes cuspidate.
32Leaf blades very broadly ligulate, mostly less than 8 (3-10) times as long as wide and over 4.5 cm wide, broadly rounded or obtuse, apex emarginate, apiculate or cuspidate.
32'Leaf blades less broad, or when broad and over 4.5 cm wide, then more attenuate toward the apex, triangular-subacute.
33Leaf blades distinctly and irregularly transversely purple-red banded, 5-6.5 cm wide, apiculate or acuminate (sometimes color-pattern lacking in var. formosa).
33'Leaf blades not with broad transverse bands.
34Leaf blades broadly rounded or subtruncate, with distinctly involute- emarginate and apiculate tip, ca. 4.5 cm wide, often with purple marks or margins.
34'Leaf blades rounded or obtuse, with apiculate or caudate, not distinctly emarginate tip.
35Leaf blades obtuse, with caudate ca. 5 cm long tip, 7-11 cm wide; sheaths pale-green, often with a castaneous band near the base at the outside. subdensely pale-brown lepidote.
35'Leaf tip apiculate or acuminate, not long caudate.
36Leaf blades (broadly) rounded, with involute-acuminate (1-2 cm) tip, subdensely appressed-lepidote and tinged with red at the underside, soon subglabrous at the upperside, except for the extreme apex; sheaths very large, more than half es long as the blade, densely dull ferrugineous- lepidote at both sides.
36'Leaf blades not with a triangular, over 1 cm long tip, not subdensely appressed-lepidote at the underside; sheaths often relatively much shorter, pale-brown lepidote.
37Sheaths often in great part castaneous at the outside.
37'Sheaths at most only with a castaneous band at the base.
38Leaf blades often with dark (sometimes pale when dry) transverse wavy pattern, broadly rounded and finely apiculate, sheaths pale-brown at the inside, densely dull brown lepidote.
38'Leaf blades evenly pale- and somewhat lustrous-green, often involute at the apex when dry, subacute or acuminate; sheaths dark purple or brown at the inside, punctulate-lepidote.
39Sheaths densely dull ferrugineous-lepidote at least at the inside, often dark brown-purple for most part at both sides, subacute or apiculate.
39'Sheaths pale-brown lepidote at the inside, leaf blades apiculate.
40Sheaths coriaceous, pale-green, concolorous with the blade at the outside, except for the narrow castaneous band near the base, with narrow chartaceous margins.
40'Sheaths chartaceous, the lower half brownish, and castaneous at the base outside, with broad pale-brown membranaceous margins.
41Sheaths dull-brown at the outside, appearing pruinose, caused by white, dark-centered appressed scales, leaf blades often tinged with red at the underside, triangular-acute or narrowly obtuse and apiculate.
41'Sheaths not appearing pruinose, often brown-lepidote or minutely)epidote.
42Sheaths very densely dark and dull ferrugineous-lepidote at both sides, leaf blades 3-5.5 cm wide, acuminate or subacute, often tinged with red and appressed-lepidote at the underside and less lepidote at the uooerside.
42'Sheaths (pale-)brown- or minutely)epidote, not dull ferrugineous at both sides.
43Leaf blades very narrowly ligulate, broadest near the base, 2.3-3 cm wide and about 12 times as long as wide, (abruptly) rounded or obtuse, with apiculate or cuspidate tip, dull (olive-) green at the upperside and mostly purple-red at the underside (underside mostly brownish and the upperside much paler when dry), sheaths brownish with pale margins. often in great part castaneous toward the base.
43'Leaf blades often much wider or when not over 3 cm wide, then much less than 12 times as long as wide, or not abruptly rounded but more attenuate toward the apex, when dry both sides often pale-green or the upper side darker.
44Sheaths in lower part very dark castaneous, and cinereously)epidote with ap- pressed white scales, with broad pale-brown margins; leaf blades erect, linear, involute at the base, triangular-subacute, somewhat lustrous green, with a wavy pattern of darker green lines (often lost when dry).".
44'Sheaths sometimes castaneous at the base but then not cinereous-lepidote.
45Leaf blades linear(-subtriangular), to 60 cm long and not over 4 cm wide, long attenuately acute, with filiform, ca. 1 cm long (finely oungent) tin.
45'Leaf blades relatively broader, narrowly triangular-ovate or ligulate, without filiform tip.
46Sheaths elliptic, relatively large, as long as to about half as long as the blade, but not always very distinct, pale-green or brown and often purple-red in part at the inside, leaf blades (3.5-)7-10 cm wide, very narrowlv triangular-ovate, triangular-acute, stramineous when dry.
46'Sheaths much shorter than the blades, leaf blades mostly not over 7 cm wide.
47Leaf blades large, ca. 60 cm or longer, and over 5 cm wide, very narrowly triangular-ovate, attenuate toward the aoex.
47'Leaf blades often much smaller, or when large then not very narrowly triangular-ovate and not attenuate toward the apex.
48Leaf blades ligulate, 4-5 cm wide, uniformly bronze to dark purple-red, pale- or reddish-brown when dry, triangular-acute or cuspidate, sheaths minutely appressed-lepidote at the outside.
48'Leaf blades often less broad, or when over 4 cm wide, more rounded or obtuse, with apiculate tip, or the sheaths dull brown-lepidote at the outside
49Leaves strongly ribbed at the underside when dry and far less at the upper-side, sheaths very densely and pale ferrugineous-lepidote at the outside, leaf blades 2-4(-6.3) cm wide, rounded, then acuminate or subacute.
49'Leaves weakly ribbed (if at all), sheaths sparsely or subdensely pale-brown lepidote at the outside, not ferrugineous.
50Leaf blades subcoriaceous, often involute at the margins when dry, paler green at the underside than at the upperside (also visible at dry material). rounded and apiculate, rarely triangular-acute.
50'Leaf blades thin and not involute at the margins, not much darker at the upperside, rounded toward the apex, then triangular-acute or acuminate, rarely apiculate.
51Sheaths more than half as long as the blade, often dark purple-red in upper half with broad whitish margins, the blades ligulate, broadest at the base. triangular-acute or acuminate.
51'Sheaths half as long as the blades or less, whitish, and often castaneous at the base, the leaf blades (linear-)lanceolate.
52Leaf blades mostly lanceolate, undulate when pressed and dried. aoiculate.
52'Leaf blades mostly obovate-lanceolate, linear-lanceolate or linear, the broadest in upper half, sheaths often longitudinally red-striate.