Monstera

Croat, Thomas B., Cedeño-Fonseca, Marco & Ortiz, Orlando O., 2024, Revision of Monstera (Araceae: Monsteroideae) of Central America, Phytotaxa 656 (1), pp. 1-197 : 9-13

Key to Monstera of Central America

1a. Spathe orange or yellow-orange at anthesis; fruits with the stylar cap orange ..................................................................................2

2a. Petioles shorter than blades; blades yellowish when dry, mostly less than 3 times longer than wide, mostly obtuse to rounded with short apiculum at apex; peduncle longer (up to 38 cm long)............................................................................. M. alcirana

2b. Petioles often about as long as blade; blades blackish, reddish, light brown or grayish when dry, mostly 3.3–3.5 times longer than broad, typically acute to acuminate at apex; peduncle shorter (10–17 cm) ........................................................ M. obliqua

1b. Spathe of various colors, never orange or yellow-orange; the stylar cap never orange.................................................................... 3

3a. Plants with pendent habit and usually lacking or with poorly-developed anchor roots on flowering branches (inflorescence always on hanging shoots); internodes mostly elongated at stem apex, generally 3 or more times longer than wide ............... 4

4a. Adult plants with leaf blades pinnatilobed.............................................................................................................................5

5a. Petiolar sheath persistent or semi-persistent, reaching base of the geniculum or base of the leaf blade; spathe tearing longitudinally at base after anthesis before falling, white within, externally yellowish-green and not pruinose; leaf blade, with 2–4 lobes per side, never perforate .............................................................................................. M. molinae

5b. Petiolar sheath deciduous, not reaching the geniculum; spathe not tearing longitudinally at base after anthesis before falling, pale pink internally, green and pruinose externally; leaf blade with 2–6 lobes per side, usually perforated........ .................................................................................................................................................................. M. tacanaensis

4b. Adult plants with leaf blades margins entire..........................................................................................................................6

6a. Stems tuberculate with scaly epidermis; petiole sheath markedly ligulate and marcescent leaving persistent fibrous remains.............................................................................................................................................................................7

7a. Leaf blades large (usually 18–59 × 15–37 cm); peduncles longer, usually equal or more than 5 cm long................. .................................................................................................................................................... M. guzmanjacobiae

7b. Leaf blades smaller (12–20 × 9–13 cm); peduncles shorter, typically up to 5 cm long........................................... 8

8a. Petioles more than 7 cm long; petiolar sheath ligulate up to 3 cm; inflorescences erect.................... M. luteynii

8b. Petioles less than 4 cm long; petiolar sheath ligulate for 3–6 cm; inflorescences pendent.......... M. tuberculata 6b. Stems generally smooth; petiole sheath non-ligulate or with poorly developed ligule (less than 1 cm long) and completely deciduous ..................................................................................................................................................... 9

9a. Leaf blade cuneate to rounded or truncated at base; peduncles shorter, up to 4 cm long ......................... M. pittieri

9b. Leaf blade cordate, subcordate, rounded, truncate to cordulate at base; peduncles more than 8 cm long..............10

10a. Primary lateral veins 15–25 per side; leaf blade generally with perforations .............................. M. wilsoniensis

10b. Primary lateral veins up to 9 per side; leaf blade usually lacking perforations................................................ 11

11a. Leaf blades 1.5–2.1 times longer than wide, up to 26 cm long; peduncle 2.5–2.6 longer than the spadix; Costa Rica (Tarrazú).............................................................................................................. M. tarrazuensis

11b. Leaf blades less 1.0–1.1 times longer than wide, usually 12.8–16.0 cm long; peduncle 1.6–1.8 times longer than the spadix; Honduras (Atlántida) ................................................................................ M. maderaverde

3b. Plants generally appressed-climbing with well-developed anchor roots on flowering branches (inflorescence typically on ascending shoots); internodes mostly short at stem apex, generally less 3 times longer than wide ..........................................12

12a. Adult leaf blade regularly pinnatifid or pinnatilobed (the lobes well differentiated and/or arranged consistently along the midrib)..................................................................................................................................................................................13

13a. Leaf blades narrow (up to 13 cm wide), usually 2.0–2.6 times longer than wide..................................... M. integrifolia

13b. Leaf blades wider (more than 13 cm wide), usually less than 2 times longer than wide ..............................................14

14a. Petiolar sheath persistent (presence of continuous tissue, whether living or marcescent, along adaxial margins of the petiole) ...............................................................................................................................................................15

15a. Petiole typically half-sheathed ..........................................................................................................................16

16a. Petioles more than 45 cm long; spadix 5.4–6.4 times longer than wide; Panama (Caribbean slope)....... M. bocatorensis

16b. Petioles less than 45 cm long; spadix up to 5 times longer than wide........................................................17

17a. Leaf blades with 6–12 pairs of lobes, mostly less than 5 cm wide; Costa Rica (Pacific slope) ......... M. croatii

17b. Leaf blades with 2–7 pairs of lobes, mostly more than 5 cm wide; Costa Rica to Colombia............ M. glaucescens

15b. Petiole fully sheathed, sometimes sheathed up to 3–6 cm before the geniculum ............................................ 18

18a. Petiole whitish or sparsely speckled with white dots; leaf blade with abundant rounded fenestrations on each side adjacent to the midrib; primary lateral veins emerge from the midrib at an angle of 80–90°; Costa Rica and Panama............................................................................................................... M. epipremnoides

18b. Petiole greenish or strongly speckled with white dots; leaf blade lacking fenestrations or with few rounded fenestrations on each side adjacent to the midrib........................................................................................19

19a. Adult leaf blade deeply pinnatifid; lobes mostly less than 5 cm wide; spadix 5.5–9.1 times longer than wide; Belize to South America (widespread)............................................................... M. pinnatipartita

19b. Adult leaf blade deeply pinnatilobed; lobes usually more than 5 cm wide ......................................... 20

20a. Stigmatophore strongly conical; Costa Rica to western Panama, at 1050–1650 m ............ M. lentii

20b. Stigmatophore cupuliform; Belize to Guatemala, Nicaragua, Honduras, Costa Rica and Panama from sea level to mostly less that 700 m ......................................................................... M. dissecta

14b. Petiolar sheath deciduous (no tissue along adaxial margins of the petiole; sometimes leaving fibers and/or remains of irregular pieces of tissue) ....................................................................................................................................21

21a. Petiole typically half-sheathed; geniculum winged; blades 1.0‒1.1 times as longer than wide; Mexico, Belize and Guatemala................................................................................................................................... M. deliciosa 21b. Petiole fully sheathed, sometimes sheathed up to 2–3 cm before the geniculum; geniculum smooth or obscure; blades generally more than 1.2 times longer than wide ....................................................................................22

22a. Adult leaf blades lacking fenestrations; spadix 6.5–9.0 times longer than wide and 2.5–3.7 times longer than peduncle ..............................................................................................................................................23

23a. Adult leaf blades with 1–6 pairs of lobes, usually more than 3 cm wide ........................... M. spruceana

23b. Adult leaf blades with generally more than 6 pairs of lobes, mostly narrow (up to 3 cm wide).............. .................................................................................................................................................... M. tenuis

22b. Adult leaf blades with or without fenestrations; spadix less than 6 times longer than wide and up to 1.6 times longer than peduncle..........................................................................................................................24

24a. Adult blade with each lobe (incompletely) separated from the next by a row of fenestrations, with the lobes sometimes cross-linked by filaments or very narrow bands of lamina often becoming broken with age .........................................................................................................................................................25

25a. Blades with 3–6 pairs of lobes, mostly connected by broader bands of laminar tissue; spathe externally pink, never longitudinally splitting at male anthesis; spadix 1.5–2.0 times longer than wide...................................................................................................................................... M. dubia

25b. Blades with more than 6 pairs of lobes, generally connected by very fine thread-like filaments; spathe externally yellowish green or pinkish, usually longitudinally splitting at male anthesis; spadix 4 or more times longer than wide........................................................................................26

26a. Petiolar sheath deciduous but leaving persistent fibrous remains; spathe externally pink...... M. filamentosa

26b. Petiolar sheath deciduous without leaving fibrous remains; spathe externally yellowish-green. M. punctulata

24b. Adult leaf blade with each lobe completely separated from the next by a single incision reaching or approaching the midrib .........................................................................................................................27

27a. Style not at all cupuliform but rather with narrow sloping shoulders, the stigma protruding well above style; Panama, 100–1600 m ............................................................................ M. donosoensis

27b. Style drying cupuliform with the margins usually as high or higher than the essentially sessile stigma, the stigma not protruding well above style; Costa Rica, 1200–1500 m .. M. monteverdensis

12b. Adult leaf blade with entire margins (with or without fenestrations) or irregularly pinnatilobed (lobes originated by tearing of the fenestrations that extend close to the margin) with a few lacerations. ......................................................................28

28a. Petiole and peduncle surface verrucose due to the presence of numerous and conspicuous brown, black, green or white pustules (lenticel-like structures visible to the naked eye) on the epidermis.................................................................29

29a. Petiole sheath deciduous, not undulate; stems and petioles with large black pustules; spathe yellowish-cream externally; Costa Rica (Alajuela, Heredia, Puntarenas, San José) to Panama (Chiriquí), 40–150 m ......... M. buseyi

29b. Petiole sheath persistent or deciduous, markedly undulate; stems and petioles with large brown, black or white pustules; spathe light green or cream externally .....................................................................................................30

30a. Petioles with greenish white (never black) pustules; base of petiole dark green; styles conical; western Panama to south central Costa Rica (Caribbean slope), 100–1200 ......................................................... M. costaricensis

30b. Petioles with brown, black and/or white pustules; styles truncate; Costa Rica (Puntarenas, San José; Pacific slope), 1100–1250 m ............................................................................................................................. M. alfaroi

28b. Petiole and peduncle smooth or rough but due to the presence of small elongated scale-like structures on the epidermis (10x magnification), pustules generally absent .............................................................................................................31

31a. Adult leaf blade distinctly membranous; mature infructescence with the pulp orange................... M. membranacea

31b. Adult leaf blade subcoriaceous or coriaceous; mature infructescence with the pulp white ....................................32

32a. Flowers with a distinctly circular stigma ..........................................................................................................33 33a. Inflorescence robust, peduncle 25–48 cm long; spathe 16–47 cm long; spadix large, 18.0– 25.5 cm long, 2.4–6.0 cm diam.; primary lateral veins 20–65 pairs; Panama (endemics) ................................................34

34a. Leaf blades lacking fenestrations; petioles light green, smooth, sheathed up to (0.36–)0.74–0.86 its total length, unsheathed portion subterete .................................................................................. M. gigas

34b. Leaf blades typically with fenestrations; petiole dark or light green, sheathed to base of the geniculum, unsheathed portion sulcate adaxially ...................................................................................... M. titanum

33b. Inflorescence medium-sized, peduncle up to 35 cm long; spathe up to 25 cm long; spadix less than 20 cm long, 2–3 cm diam.; primary lateral veins up to 25 pairs............................................................................35

35a. Leaf blades generally narrowly lanceolate, generally more than 2.1 times longer than wide..............36

36a. Petiole whitish to speckled with white dots; adult leaf blade perforated or not; spadix 4.7–5 times longer than wide, 0.6–0.9 times as long as peduncle; style conical; Costa Rica and Panama........... .................................................................................................................................... M. integrifolia

36b. Petiole green; adult leaf blade never perforated; spadix 2.1–4.6 times longer than wide, 0.2–0.4 times as long as peduncle; style rounded; Panama (Coclé).............................. M. coclensis sp. nov.

35b. Leaf blades lanceolate-ovate to broadly lanceolate, ovate, oblong or elliptic, typically less than 2.2 times longer than wide..........................................................................................................................37

37a. Petiolar sheath deciduous (no tissue along adaxial margins of the petiole; sometimes leaving fibers and/or irregular tissue pieces remains) ...........................................................................................38

38a. Leaf blades 1.3–1.7 times longer than petiole; fenestrations usually numerous; peduncle short (up to 12 cm long); spadix 1.1–2 times as long as peduncle; Mexico to Guatemala, El Salvador, Honduras and Nicaragua...................................................................................... M. siltepecana

38b. Leaf blades 0.7–1.3 times longer than petiole; fenestrations few; peduncle 12–20 cm long; spadix 0.5–0.8 times as long as peduncle; Panama (endemics) ...............................................39

39a. Leaf blades small, up to 25.5 × 16.0 cm; primary lateral veins up to 8 pairs; style truncate; Panama (Cerro Jefe) at 980 m ...................................................... M. harrisoniorum sp. nov.

39b. Leaf blades large, typically more than 26 × 16 cm; primary lateral veins up to 20 pairs; style strongly conical; Panama (widespread), at elevations of 100–1600 ............. M. donosoensis

37b. Petiolar sheath persistent (presence of continuous tissue, whether living or marcescent, along adaxial margins of the petiole)........................................................................................................40

40a. Petioles and leaf blades glaucous adaxially (when fresh); fenestrations numerous; peduncle short, up to 6 cm long; spadix 1.6–3.3 times longer than peduncle; Mexico (Veracruz) ....... M. florescanoana

40b. Petioles and leaf blades green; fenestrations usually absent, peduncle generally more than 9 cm long; spadix 0.6–0.9 times as long as peduncle; Nicaragua to Panama............. M. standleyana

32b. Flowers with a strongly linear stigma ...............................................................................................................41

41a. Petiolar sheath deciduous (no tissue along adaxial margins of the petiole; sometimes leaving fibers and/or irregular tissue pieces remains)...................................................................................................................42

42a. Leaf blades generally narrowly lanceolate, 2.1–6.0 times longer than wide; fenestrations absent ......43

43a. Peduncle more than 12 cm long, 3–8 times longer than petiole; primary lateral veins up to 5 pairs; style truncate; Panama (Comarca Guna Yala) ................................................................. M. minima

43b. Peduncle typically less than 15 cm long, 0.2 times as long as petiole; primary lateral veins 4–25 pairs; style prolonged and constricted in the middle; Costa Rica and Panama.............. M. anomala

42b. Leaf blades lanceolate-ovate to broadly lanceolate, ovate, oblong or elliptic, typically up to 2 times longer than wide; fenestrations usually present, rarely absent .............................................................44

44a. Primary lateral veins up to 7 pairs; Panama (Comarca Ngäbe-Buglé)............ M. ngabensis sp. nov. 44b. Primary lateral veins numerous, more than 14 pairs ......................................................................45

45a. Spathe pink to salmon-pink at anthesis ....................................................................................46

46a. Spathe pale pink internally, not becoming torn at base nor reflexed when open; petioles smooth; Costa Rica (Buenos Aires, Pacific slope in the Cordillera of Talamanca), 2000– 2100 m ........................................................................................................... M. mittermeieri

46b. Spathe dark pink or salmon-pink internally; petioles smooth or warty; Costa Rica to Panama, 800–2300 m ........................................................................................ M. oreophila

45b. Spathe of various colors, never pink to salmon-pink ...............................................................47

47a. Leaf blades 35–45 cm wide, 1.2–1.5 times longer than petiole; Mexico (western Chiapas) to Belize, and Guatemala; elevations range from 0–200 m .................... M. acacoyaguensis

47b. Leaf blades up to 30 cm wide, 0.9–1.0 times as long as petiole ........................................48

48a. Spadix 3.6–4.8 times longer than wide, 1.0–1.2 times as long as peduncle; Costa Rica and Panama, 1900–2300 m .............................................................................................. .................................... M. tablasensis M.Cedeño in Cedeño-Fonseca et al. (2022: 162)

48b. Spadix 4.8–9.2 times longer than wide, 0.7–0.9 times as long as peduncle; from sea level to 975 m ...............................................................................................................49

50a. Petiole dark green, smooth (rarely asperous with white pustules); primary lateral veins bifurcated or trifurcated or not; spathe white externally; widespread.............. .............................................................................................................. M. adansonii

50b. Petiole white-dotted, smooth with few dark pustules in base; primary lateral veins never bifurcated or trifurcated; spathe white-yellowish externally; Costa Rica and Panama (Pacific slope)............................................................................ M. limitaris

41b. Petiolar sheath persistent (presence of continuous tissue, whether living or marcescent, along adaxial margins of the petiole).................................................................................................................................51

51a. Petiole usually half-sheathed, sometimes 5–15 cm beyond the middle; leaf blades glaucous abaxially (when fresh); Panama (Caribbean slopes of Bocas del Toro and Veraguas)................... M. bocatorensis

51b. Petiole fully sheathed, sometimes sheathed up to 2–3 cm before the geniculum; leaf blades never glaucous ................................................................................................................................................52

52a. Spathe pink to salmon-pink at anthesis; Panama (Chiriquí Province, Comarca Ngäbe-Buglé, and Veraguas) at 900–1500 m .................................................................................................. M. gentryi

52b. Spathe of various colors, never pink to salmon-pink .................................................................... 53

53a. Petiole asperous; petiolar sheath involute; leaf blade up to 10 cm wide; peduncle 1.0–1.1 times as long as petiole; spadix 0.3–0.4 times as long as peduncle; Costa Rica (Golfito) at 50–100 ... M. gambensis

53b. Petiole smooth; petiolar sheath non-involute; leaf blade more than 10 cm wide; peduncle 0.1– 0.6 times as long as petiole; spadix 0.7–2.0 times as long as peduncle ...................................54

54a. Peduncle short, up to 12 cm long; spadix 0.9–2.0 times longer than peduncle; Mexico to Guatemala, Belize, Honduras, and Nicaragua................................................. M. acuminata

54b. Peduncle more than 12 cm long; spadix 0.7–1.3 times as long as peduncle......................55

55a. Spadix up to 14 cm long, 0.9–1.3 times as long as peduncle; Costa Rica and Panama at 1650–2010 m .................................................................................................. M. juliusii

55b. Spadix more than 14 cm long, 0.7–0.8 times as long as peduncle; Mexico and Belize at 100–1500 m ................................................................ M. egregia Schott (1864: 53–54)