Major trends of evolution in palms

From the diversity found among palms the following evolutionary trends are suggested:habit: from sympodial to monopodial;size: from moderate toward large and also toward small;stem: from unbranched to dichotomously branched, from little to much sclerenchyma, from short to elongate internodes;leaf: from an undivided eophyll to a palmate, costapalmate, pinnately ribbed or pinnate blade; from undivided and plicate to divided along the adaxial rib (“induplicate”) or along the abaxial rib (“reduplicate”); from pinnate to bipinnate or to pinnae onceor twicedivided longitudinally; from sheath split opposite the petiole to sheath tubular; from marcescent to deciduous; from central vascular bundles of the petiole with a single phloem strand to two phloem strands;inflorescence units: from moderately branched to spicate or less frequently to more diffusely branched, from one unit per leaf axil to more than one per axil, from among the leaves to below them or to above them in a compound terminal inflorescence, from pleonanthic to hapaxanthic;prophyll: from completely to incompletely encircling the peduncle, from incompletely to completely sheathing in bud;bracts: from conspicuous to small or absent at maturity, first peduncular bract from tubular and open at the apex to completely enclosing the inflorescence in bud, and then from ungrooved to deeply plicate;flower arrangement: from solitary, pedicellate, bracteolate flowers to a sympodial cincinnus of 2 or 3 or more, or to a short monopodial axis of 2–4 or more;bracteoles: from sheathing and prophyllate to completely closed or to incompletely developed or absent;flowers: from bisexual to unisexual, then associated with polygamy or monoecism to dioecism;perianth: from trimery to dimery or tetramery to decamery or to reduced and monochlamydeous;sepals: from distinct and imbricate to connate or separated;petals: from distinct and imbricate to valvate, or strongly imbricate, or connate; from small and ovate to large and variously shaped, or to small;stamens: from 6 to 3 or to more than 6 (to 950+);filaments: from relatively slender and distinct to broad and thick, and often connate or adnate to the perianth or both;staminodes: from stamenlike with abortive anthers only, to short teeth, or to a cupule at the base of the ovary, or to absent;pollen: from monosulcate to trichotomosulcate to dicolpate to monocolpate, diporate, or triporate;gynoecium: from apocarpous to syncarpous, from thin walls to thick, variously specialized walls;carpels or locules: from 3 to 2-1 or to 4–10;ovules: from moderate to small or to large, from anatropous to hemianatropous to campylotropous to orthotropous;pistillode: from only slightly modified from the gynoecium to vestigial or lacking or rarely to prominent;fruit: from fleshy to dry and fibrous;endocarp: from little differentiated or thin, to thick and hard, and sometimes with a pore or operculum over the embryo;seed: from moderate to small or to very large, from entire to dissected, bilobed, or perforate;endosperm: from homogeneous to invaginated or ruminate;germination: from remotetubular or -ligular to adjacent-ligular;chromosome complement: fromn = 18 ton = 17, 16, 15, 14, 13.