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)