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678 Annals of the Missouri Botanical Garden are solid green on both surfaces. There are consid- with the staminate flowers at the apex and the piserable differences in the nllmler of inflorescences tillate flowers at the base. The spadix of Dieffenper axiln ranging from solitary on a number of spe- bachia is usually shorter than the spathe by 1-3 cies at least part of the time or up to eight per axil cm (Fig. 2B). The spadix is contained within the as with D. concinna. In any population the number spathe, and is more or less straight or weakly of inflorescences per axil may vary. Studies made curved (Fig. 8F) at anthesis, rather than being with D. oerstedii in Costa Rica (Valerio, 1984) prominently protruded forward. Some species have showed that this species produced primarily one or the spadix protruded forward at anthesis, such as two inflorescences per axil. D. burgeri (Fig. 4C), D. crebripistillata (Fig. 7C), D. horichii (Fig. 13E), D. wendlandii (Fig. 26C), and SIATHE D. seguine (Fig. 23E). The last species, which ranges throughout the West Indies, has a spadix that Each spathe in a cluster of inflorescences in notably protrudes and is cylindrical, rather than ta- Dieffenbachia is subtended by linear-lanceolate pered to the apex as in the remaining Central bracteoles, each of which are unribbed. The brac- American species (Fig. 23F). Diefienbachia seguine teoles are typie ally about as long as the peduncles, also has a spadix (Fig. 23) that is caught in the but can sometimes be shorter or longer. They are protruded position when the spathe re-closes. In somewhat mar( ese ent. contrast to D. seguine, all of the (3entral American Spathes of llieffenbachia are uniforrnly green, species have spathes that close normally with the though the inner surface tends to be somewhat palspadix withdrawing inside of the spathe. er than the outel surface and frequently much Like other members of the Philo(lendroideae, the glossier. The OUtUl spathe surface is typically sespadix in Dieffenbachia is divide(l up into a fertile miglossy to weakly glossy. Sometimes the inner surstarninate section at the apex, a sterile section lying face of the spathe is somewhat whitish on the inside beneath the fertile staminate )oltionX and the pisnear the tip. tillate portion (Figs. 2B, 7, 18! 2?.5). The lowermost The spathe of Illost Diefenbachia is only weakly section, as with all Araceae witll llllisexual flowers, constricted alsove the spathe tube (Figs. 7A, 16D, is the pistillate section. Typie ally lhe pistillate por- 20F, 22E, 2^-3kJ! 2zlt 25F). When the entire spathe tion and the staminate portion (lle of roughly equal is fully flattene(l, lhe tube portion is considerably lengths, but the length of the stex ile eiegment (when wider (Figs. 21S, I SH, 22F, 23F) and the spathe is apparent) is highly variable lsolll ill terms of length gradually tapere(l from the lower 1/4 to the usually and the degree to which stamino(lia and pistillodes acuminate apex (Fig. 23F). Sometimes there is a are dispersed on it (Figs. 2B, 4(3! .5l), 7, 15H, 18D, weak central (onstriction. The point of maximum 23F, 25G). In most cases the [)istillate region is c onstriction c orl esponds to the sterile section of the slightly longer than the staminclte. spadix betweell the fertile staminate flowers and the The fertile staminate portion is somewhat cylinpistillate flowers. droid to spindle-shaped, broa(lest ill the middle and At anthesis tle spathe of Diefenbachia is open weakly tapered toward both en(ts, being bluntly to about the middle (Figs. 5B, 7A, 13E, 16D), or rounded at the apex. The fertile rllale flowers are somewhat below the middle, lgut does not open as compacted and sub-rounded or with angular marwidely as that of Philodendron. At anthesis the gins (Figs 2E, 5G). As the spa(lix approaches anspathe blade is wider than the tube. Typically only thesis the synandria loosen ancl the anthers become the staminate portion of the spadix is visible at anvisible between the synandria. 'roward the base of thesis but sometimes, as in D. crebripistillata, a porthe staminate portion of the spa(lix, the flowers are tion of the pistillate spadix is also exposed. Closure somewhat more irregular in size and shapen but do of the spathe after anthesis is sometimes not comnot become radically different as in the case of plete, with the margins of the spathe meeting irreg- Philodendron and Xanthosoma, where the lowerularly. At anthesis the blade of the spathe is usually most male flowers are sterile and swollen. In conarched somewhat forward, hooding the spadix trast, Dieftenbachia relies entirely on club-shaped slightly. For some species, such as D. crebripistilstaminodia surrounding the pistils (Figs. 5E, 14C). lata, the spathe may be recurled at anthesis (Fig. The lowermost staminate flowers are smaller or very 7C). irregular in shape, sometimes showing signs of two SPADIX or more flowers fused together. Sometimes the uppermost pistils are reduced, apparently sterile, and Flowers of Dieffienbachia are unisexual and na- surrounded by sterile male flowers (Fig. 15H). Apked, dispersed on the spadix- in the typical manner parently the lowermost staminate flowers are also
Volume 91, Number 4 2004 Croat Revision of Dieffenbachia more attractive to beetle pollinators, since only the apparently absent, with the fertile staminate and lowermost flowers are eaten (Fig. 1B). fertile pistillate portions essentially contiguous. The length of the sterile portion of the spadix is here ANDROECIUM defined as that portion which lies between the lowermost functional androecium and the uppermost Staminate flowers consist of 4 stamens united functional pistil regardless of the presence of pisinto a 4- or 5-sulcate truncate synandrium (Figs. tillodes and staminodes along its length. However, 2E, 5G, 23G, 26E). The apex of the synandrium the sterile portion of the spadix is usually quite often has a minute slit or an equidistant series of obvious since a significant proportion of the sterile 3 minute slits connected at the center. Upon drying section is devoid of flowers. The axis of the sterile the apex of the synandrium may become wrinkled portion is typically convex as if the terete axis of along the margin and may also have a concave sur- the spadix (now fused) was half sunken into the face. The anthers are contiguous or nearly so, af- leafy tissue of the spathe. fixed near the upper edge of the synandrium. The thecae are obovoid to cylindroid, opening by apical PISTII,I,ATE SPADIX slits just below the upper edge of the synandrium. The pollen is dispersed in slender, subterete filaments and typically projects up to 1 cm above the surface of the synandrium. When the stamens are at anthesis, the shedding pollen can completely fill the now closing spathe (Fig. 5F). The pistillate portion of the spadix is fused throughout its entire length to the spathe. What appears to be a stipe is readily apparent at the base. The pistillate flowers rarely extend very close to the base of the spathe (Fig. 4C). After the presence or absence of a sterile segment in the spadix, the POLI,EN number and disposition of the pistils is perhaps the Pollen of Dieffenbachia is released in monads most important taxonomi( character in the infloresthat are inaperturate, subisopolar to virtually polar, cence. Unlike many genera in the Philodendroi(leae boat-shaped-ellipti( to oblong, or nearly spherie al. that have the pistillate flowers closely aggregate(l They are bilaterally symmetrie al or radiosymmetrie on the spa(lix, the pistillate flowers of DiefJenbachia (Grayum, 1992). are moderately dispersed on the spadix. The degree Dieffenbachia pollen is moderately large for Ar- of (lispersal on the spadix is in itself different from aveae, ranging from 54 to 99 1lm (as in D. oerstedii) spee ies to spee ies. There are generally only 2 or 3 and avelaging 79 11m. Exine sculpturing is psilate pistils aeross the width of the spadix axis (regardto obs(urely verrueulate (as in D. oer.steflii) an(l/or less of whether they are lined up or not). Rarely, sparingly punctate-foveate to densely foveate with as in the ease of D. killivii, there up to 6 pistils scattered compound foveolae (as in D. pittieri and visible across the width of the spadix. At the op- D. seguine). Grayum (1992) pointed out that the posite extreme, D. Iongispatha sometimes has a solcompound foveolae found on the pollen of D. pittieri itary row of pistils across the spadix axis. The arand D. seguine resemble those of Chlorospatha rangement of the pistils is generally quite irregular, croatiana Grayum. lacking any obvious equidistant spacing or alignment in rows, but sometimes a series of pistils STERILE SPADIX SECTION might be arranged in a loose row (as in D. killipii) or even in a broad arc across the width of the spa- Dieffienbachia typically has a nearly barren sec- dix. tion of the spadix lying between the fertile stami- Pistils are 2- or 3-carpellate, sometimes l-carnate portion at the apex and the pistillate portion pellate, sessile, depressed-globose to depressedat the base (Figs. 5D, 23F). This section occurs in ovoid, pale green, semiglossy, and smooth or 2- or the area where the spadix first becomes free from 3-lobate. The stigma is a 2- or 3-lobate cushionthe spathe. Only rarely is the transition between like layer that covers the entire apex of the pistil. the fertile staminate and the sterile }ortion of the The stigmatic papillae are orange or yellow. The spadix clearly defined with the fertile flowers papillae are close, dense, and moderately short, abruptly ending on a clear flowerless sterile portion. similar to those of Philodendron, but appear less Instead, there is usually an assortment of sterile interspersed with the gelatinous matrix that is so male flowers toward the apex of the sterile segment common on the stigmas of that genus. The stylar (Fig. 7E). Less frequently there are pistillodes in region is inconspicuous. With the stigma removed, the lower half of the sterile segment. In D. beachi- the surface is truncate or broadly sulcate with a ana and D. killipii (Fig. 15H) the sterile section is solitary medial or near-medial pore. Ovules are 679
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760 Ez D. fosten (0, -8 ' ; < * ( \
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762 , C72 89° 86° 83° 80° 77°
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