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Project Name Data (Last Modified On 11/29/2012)

Flora Data (Last Modified On 11/29/2012)
Description More or less massive and succulent, usually leafless terrestrial or epiphytic plants. Stems usually (except in Pereskia) phylloid and jointed, the joints elongate to suborbicular, terete to angled or flattened, the nodes with axillary areas (areoles) usually armed with spines, slender barbs (glochids) or hairs in various numbers and combinations, occasionally naked. Leaves alternate and laminate in Pereskia, but in the other genera minute and fugacious, or wholly lacking. Flowers pedunculate and in 1- to several-flowered panicles in Pereskia, in the other genera solitary and sessile, very large to very small, frequently nocturnal, epigynous (perigynous in Pereskia); perianth salverform or infundibuliform to rotate, with or without a conspicuous tube, monochlamydeous, actinomorphic when erect and more or less zygomorphic by position when horizontal or pendulous, the segments petaloid, usually white to red or yellow, relatively few to exceedingly numerous, the inner broader and more petaloid than the outer and lower, the tube naked or with bracts or areoles or both; stamens usually very numerous, with elongate filaments, inserted within the perianth tube or upon the ovary in rotate flowers; ovary inferior (sub- inferior in Pereskia), 1-celled, with few to several parietal placentas usually bearing numerous ovules, the style more or less elongate and filiform, with an elaborate radiate terminal stigma. Fruit a berry usually with numerous seeds immersed in succulent pulp. The Cactaceae are a typically Western Hemisphere family, with only the genus Rhipsalis, the Mistletoe Cactus, doubtfully indigenous to the Old World. Species of Opuntia, however, especially 0. ficus-indica, have been introduced since very early times and become naturalized in Africa and elsewhere. The genera vary in number according to the interpretation of individual authors, from only 20 (K. Schumann, in Engl. Nat. Pflanzenfam. III: 6. 1894) to over 100 (cf. Britton & Rose, in Carnegie Inst. Publ. No. 248. 1919-1923). Much criticism has been made of the numerous segregate genera proposed by Britton and Rose and much undoubtedly remains to be learned of their natural relationships. In Panama, however, their genera usually are quite readily distin- guishable into apparently natural groups; consequently they are adopted here without major modification. The controversy of "tlumpers vs. splitters" in dealing with cacti dates at least as early as 1813, when Sims (in Curtis's Botanical Maga- zine 38: sub pl. I557) inveighed against Haworth's generic segregates and advo- cated the return of both Cereus and Opuntia to the Linnaean genus Cactus, now long abandoned. In humid Panama the cacti bear little resemblance as a rule to those so familiar in the landscapes of the arid regions of the United States and Mexico. Here they are mostly clambering semilianes on rocks, or epiphytes, with only two or three species of Opuntia and Nopalea, possibly introductions, to represent the Prickly Pears. Pereskia scarcely resembles a cactus at all, with its shrubby or tree-like habit, terete stems, and conspicuous leaves. Cacti of the Rhipsalis and Cereus alliances often are encountered in Panama, but all to frequently in a sterile condition. This, together with the difficulty of preparing such succulent plants for the herbarium, accounts largely for the very few specimens found in museums. Actually, the species are not at all as rare as the few citations would indicate. The total number in Panama must be considerably greater than that of the present account.
Key a. Stems not phylloid; leaves conspicuous and laminate, deciduous; flowers pedunculate, often clustered, perigynous . ,,,.,,,,,,,,,,,,,,,,,,,,,-,,,,.,,,,,.1. PERESKIA aa. Stems phylloid; leaves lacking or inconspicuous and fugacious; flowers sessile, solitary, epigynous. b. Stem joints suborbicular to broadly linguiform in our species, entire, the areoles amphigenous, with glochids; perianth rotate to campan- ulate. c. Petals erect, shorter than the stamens; stamen filaments not sensitive, erect at anthesis; style enlarged near the base into a disci- form stylopodium. ,-,,..,..,,,,,, .. ,,,.. ,.. ,,..,.. ,,,,.2. NOPALEA cc. Petals spreading, longer than the stamens; stamen filaments sensitive, spreading at anthesis and inflexing upon stimulation; style only slightly thickened toward the base.,,.,,,,,,,,,,,,,,,,,,,,- ,,,,,,.,,.3. OPUNTIA bb. Stem joints elongate, terete to angled, or flattened and undulate or lobed, the areoles marginal upon the flowering joints, without glochids. c. Flowers very large, rarely mediocre, with a definite perianth tube; stamens adnate to the perianth tube. d. Flowering stem joints ribbed or angled, the areoles usually more or less spiny and bristly. e. Stem joints usually 5-angled, with numerous large spines; plants terrestrial, the stems erect at first, but finally deflexed and rooting at the tips; perianth tube much longer than the segments, the adnate bracts inconspicuous and fugacious but with prominent spiny areoles.-,,,,,,,,,... 4. ACANTHOCEREUS ee. Stem joints usually 3-angled, with inconspicuous and infrequent spines, or unarmed; plants clambering upon rocks or epiphytic, rooting laterally from the stem joints; perianth tube shorter than the segments. f. Flowers very large; perianth tube with conspicuous and persistent bracts, not bristly or hairy.-.,,,,. ,,.,,,,.5. HYLOCEREUS ff. Flowers mediocre; perianth tube with inconspicuous and fugacious bracts subtending conspicuous persistent bristly or hairy areoles..,,-.,,..,,, ..,..,,..,,,,, ..,, ..,.....6. WEBEROCEREUS dd. Flowering stem joints flat and leaflike, lobed or undulate, the areoles naked to minutely puberulent. e. Flowers large, with an elongate perianth tube, the segments very numerous; stamens very numerous, the filaments many times longer than the anthers; stigma lobes numerous-................ 7. EPIPHYLLUM ee. Flowers mediocre or relatively small, with a rather short peri- anth tube, the segments about 10-20; stamens about 20-30, the filaments not greatly longer than the anthers; stigma lobes 3-5 -..-.-.. 8. WITTIA cc. Flowers very small, without a definite perianth tube or the segments quite free; stamens adnate (in our species) to the margin of the hypanthium; flowering stem joints terete or essentially so, naked or with bristly or hairy areoles .,,,,,,, . 8. RHIPSALIS
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