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. . . n . . . 680 Annals of the Missouri Botanical Garden anatropous, one per locule. Each pistil is surround- were sterile, varying from 1 to 17 per infructesced by 4 or 5 claviform, fleshy, white staminodia. ence. The staminodia may be fused somewhat at the base, Germination of seeds is usually prompt if the often forming a cupuliform structure around the mesocarp is first removed. Valerio (1984) found that base of the pistil. Individual staminodia are sub- naked seeds of cleaned berries of D. oerstedii began cylindrical, commonly somewhat flattened toward to germlnate wltnln I our days ln a germlnatlon the base and usually enlarged, sometimes almost chamber. The percentage of seeds germinating subglobular at the apex. Staminodia typically are ranged from 77.3Wo to 100% for different infrucerect-spreading or erect, vary considerably in tescences (averaging 91.7Wo). However, berries left length, but are almost invariably longer than the intact usually did not germinate, but remainded vipistils, usually 2-5 mm long, and held well above able for up to 90 days. the pistils. Valerio (1984) also reported that although 82Wo of the 729 berries studie(l were green, the remain- MORPHOLOG Y () F1 FRUITING STRUCTURES der were red or yellowish. All seeds produced only eN( l X AND FRUIT albino plants. Germinatiorl lates for both the green seeds and the abnormal seeds were the same, but While the intlorescences are always first erect, the albino plants perishe(l. His studies with seed they quickly be(ome reflexed after anthesis. This germination of D. oersteelii, as well as observations is probably important to successful development of of other plants in the fiel(l le(l him to conclude that the infructescen(e as it prevents the spathe from plants of this species re(uile(l between five and six filling with rainwater and thus possible decay. years to reach reproductivf age. Fruits develop within the re-closed spathe, which Fruit maturation is nollally a slow process in often turns yellow, pale to bright orange, or red as Dieffenbachia, requiring ll) to nine months in the fruits begin to nlature. The spathe enlarges some- case of D. nitidipetiolat(l (Young, 1986) (reported what during the (ourse of maturation, an(l finally as D. Iongispatha). Valf gio (1984) reported that begins to reflex along the middle, especially the fruit maturation in D. *ser.st(elii was approximately portion that is fsed to the spadix. In the l)rocess one year. Valerio (1984) sllgt,ested that the seeds most of the margins of the spathe slough off, leaving of Dieffenbachia are l)i(l-(lispersed because the just the fruiting spadix. The spadix remains arched seeds will not germinate [Xless the fruit mesocarp backward with lhe bright red to orange-re(l berries is first removed. At mallll ily the mesocarp of Diefheld somewhat apart by the recurving proe ess and fenbachia berries is pasty (l](l somewhat sweet. The displayed against the generally pale remains of the fruits would appear to l)e lllo;t suitable to bird disspathe (Figs. 1D, 4D). persal, being colorful a](l 11aving only a thin layer Although fluit develops with self pollination, of edible portion availal)le. 'I'he seeds are soft and fruit and seed size are greater when the plants are could easily be destroye(l l)y (hewing, so effective out-crossed (Young, 1986). Since Dieffenbachia animal dispersers are plol)al)ly just removing the flowers are nake(3 all protection of the flowers must pericarp and thin mesocal ). F ruits of DielJenbachia be provided hy the spathe. In the manner of many have been observed bei], eaten by white-faced other genera in the Philodendroideae, the spathe monkeys, Cebus capucinll.s (J. Oppenheimer, pers. re-closes ovel the female flowers after pollination. comm.), but it is not knowr] whether they are the In most cases, protection of the developing fruits primary dispersal agents, sillve cebus monkeys are after pollination is provided by the thickness of the known to be generalists ir] lheir eating behavior (J. spathe, as is true of other aroid genera such as Philodendron, but in Dieffenbachia protection is Oppenheimer, pers. comm.). also provided by toxins in the sap, which may burn the mouth of any animal eating it. However, the FLOWERING BEHAVIOR ANI) ItOLLINATION pericarp and mesocarp of the berry appear to have Dieffenbachia populations tend to be aggregated, no injurious effects when eaten and apparently lack perhaps due as much to the vegetative reproduction the sallle toxic effects found elsewhere. of the stems as by local germination of seeds. A Generally, most pistils of an inflorescence are single clone may have many stems, but relatively pollinated and develop into fruits, but the number few stems flower in a given year, and the number produce(l per plant is variable. Studies in Costa of inflorescences open on a given day is few (Young, Rica on D. oerstedii (Valerio, 1984) showed that the 1988b). Inflorescences borne on a single stem genfruits varied from 13 to 43 with an average of 26 erally do not anthesally overlap, thus there is little per plant. Valerio also reported that some berries potential for geitonogamy (Young, 1990). For D. ni-
Volume 91, Number 4 2004 Croat Revision of Dieffenbachia tidipetiolata (reported as D. Iongispatha in Young, to close and the staminate flowers are emitting pol- 1988b) a reproductive stem may have two to seven len in long filaments (Fig. 5F). In order to leave the inflorescences during a single growing season, ma- inflorescence the beetle must literally wade through turing at intervals of 3 to 12 days (Young, 1986). pollen, ensuring that it will be covered with pollen For D. oerstedii there may be between one and four before flying away to the next receptive infloresinflorescences per axil. Valerio (1984) reported that cence. plants which produced a solitary inflorescence (34 While some Dieffenbachia species, perhaps of the 83 plants studied produced inflorescences) most, have spathes that remain open only 24 hr. did not develop fruit. Valerio was unable to ascer- (based on my observations in the field), the pollitain whether this was due to a lack of pollinators nation event for D. nitidipetiolata (reported by or age of the plants. Young as D. Iongispatha) involves three days The pollination biology of Dieffenbachia has (Young, 1990). Inflorescences of this species open been studied (Croat, 1978, 1983b; Valerio, 1984; in the evening of the first day, but the spadix is not Young, 1986, 1988a, 1990). It has long been known initially receptive. On the evening of the second to aroid workers that Dieffenbachia and several oth- day the stigmas become receptive (about 17:30) er aroid genera, e.g., Philodendron, some Syngon- and the spadix temperature increases to 4°C above ium, and Xanthosoma, are visited regularly by large ambient temperature (Young, 1990). It is at this scarab beetles (Coleoptera). Young (1986, 1990) time that beetle pollinators arrive, and they enter found that D. nitidipetiolata (reported as D. Iongis- the spathe where they generally persist for another patha) is pollinated mostly by beetles of the genus full day, departing on the evening of the third day. Cyclocephala (Scarabaeideae, Dynastineae) or more Young (1990) found that for most days there were infrequently by the genus Erioscelis, also a dynas- fewer than four inflorescences open and in ferrlale tine scarab. Other visitors, including Diptera, He- phase at any one time in an area of 700,000 rrl2. In miptera, Dermaptera, Thysanoptera, an(l nitidulid her stuLlies at l, Selva in Costa Riea she foun(l beetles (Coleol)tera, Nitu(luli(lae), I)rove(l not to that l)eetles flew I)etween 1 an(l 68() m (averaging ( arry )ol]en and were deeme(l ly Young nol to I)e pollinators (Young, 199()). 8.S m) ))etween (onse( utive visits to 19. nitifli/)etiol- t(l (leporte({ as 1). lest7.gis/)(lth(l). ()ther monoe(ious aloid generae su(h as; l'lliles- Beetle pollination ot l)ie/>nlselehiel is not speler1(1ror1 an(l X(lethc)somfl, are krown to le }eetle (ies-s,^)e(ifi(. Nine (liffeellt s(arat) teetle sy)e(ies [)ollinate(l an(l provide foo(l })y meal-]S; of oil-ri( h of (Sycloee)lzfll(l as wel l as Frioseeli.s ( ollltnl)ie (l Ensterile male flowers. ln l)iet/erll)(l(hi(l the foo(1 re- (IIO(I; WUlP fOllrl(l to )OIlitlAtC 1). niti/i/)cJt.iolfltel (rewal(l (onsists of the l)rotein-ri(h (lul-shale(l sta- [)orted I)y Young as I). lotZgisisfithfl) at the l,a Selva mino(lia surroun(ling ea( h female flower (Young, ltesel ve i] Costa lti( a (Young, ] 986). Still, lliet 1986, 199()), I)ut the lmeetles have also })een seen fenhach ia sI )ecies l l o(l u( e (lifferent s( ents an(l (liffeeding on the lowermost poltion of the fertile sta- ferentially attl ae t pal tie ular leetle spee ies (G. minate portion of the sleadix. An indication that the Se hatz, pers. ( omm.). staminodial foo(l source is impoltant to the beetles Be(ause of the loose relationship between the an(l prefelred over other flolal parts, is that the pollinators ancl any olle species of DiefWenbachia, beetles will leave an inflorescence. hybridization (loes occasiollally occur (Young, pers. The production of scents during flowering is fa- (omm.). It is known that seeds from hybrid plants cilitatecl by the thermogenic behavior of the spadix, do germinate and produce viable F1 plants. It has which may increase as much as 4°C during anthesis not yet been determined if this F1 generation is (Young, 1990). Scent production coincides with the capable of reproducing sexually. Still, this phenomflight activity of the scarab beetle pollinators enon of hybridization might explain the many dif- (Schatz, 1990). Active movement of pollinators is ferent, seemingly related, but distinct, populations usually at dusk, seemingly in direct paths to an of D. nitidipetiolata that occur in some regions, open inflorescence. Beetles arrive at the inflores- such as the Rio Guanche region of Colon Province cence by first landing on the spadix (Young, 1990), in Panama. Since asexual reproduction is so prevthen entering the lower tube portion of the spathe alent in Dieffenbachia, occasional hybridization folwhere the pistillate portion of the spathe is at an- lowed by vegetative reproduction might explain thesis. Beetles typically remain in the inflorescence these patterns of variation. for 24 hr. after their arrival. While in the spathe the beetles mate and eat the nutritious staminodia PHENOLOGY (Young, 1986) surrounding the pistils. Beetles de- Some species of Dieffenbachia are in flower all part the following day as the inflorescence begins year-round. In general, more flowering takes place 681
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