Foliar Scales of the Subfamily Pitcairnioideae (Bromeliaceae)

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Abstract
Foliar scales of 45 species representing seven pitcairnioid genera were examined with light microscopy and scanning electron microscopy (SEM). Scale form varies among pitcairnioid genera in: 1) number of central disc cells; 2)type of arrangement of cells around the central disc; 3) organization of marginal wings; 4) gross structure and symmetry of scales; and 5) their distribution, arrangement, and density. Thick, opaque, marginal wings of foliar scales and their arrangement in several overlappig periclinal tiers, evident from several taxa (e.g., Abromeitiella, Deuterocohnia, Dyckia) have not been noted previously in the subfamily. Pitcairnioid scales differ from those of the tillandsioids in the absence of an orderly increase in the cells of the peripheral rings. Funnel-shaped scales and their arrangement in linear rows are common to Pitcairnioideae and Bromelioideae. Several scale features support two generic groups of Pitcairnioideae recognized also on the basis of leaf anatomy. Scale characteristics appear to have evolved differently in mesic and xeric environments. Functional and developmental aspects of the pitcairnioid foliar scales appear to be rewarding areas for further research.