Recircumscription and taxonomic revision of Siderasis, with comments on the systematics of subtribe Dichorisandrinae (Commelinaceae).

A new circumscription and a total of six microendemic species, four of them new to science, are herein presented for Siderasis, based on field and herbaria studies, and cultivated material. We provide an identification key to the species and a distribution map, description, comments, conservation assessment, and illustration for each species. Also, we present an emended key to the genera of subtribe Dichorisandrinae, and comments on the morphology and systematics of the subtribe.

Taxonomic revision of Neotropical Murdannia Royle (Commelinaceae).

This study provides a taxonomic revision for the Neotropical species of the genus Murdannia. Six species are recognized as native, including a new species and a new combination, while two Asian species are recognized as invasive. We present an identification key, a table summarizing the morphologic differences among the species, a new synonym, six lectotypifications, a distribution map, and descriptions, comments and photographic plates for each species. We also provide comments on the morphology of the Neotropical species of Murdannia, comparing them with the Paleotropical species, and a discussion of inflorescence architecture in the genus as a whole.

Pointillist structural color in Pollia fruit.

Biological communication by means of structural color has existed for at least 500 million years. Structural color is commonly observed in the animal kingdom, but has been little studied in plants. We present a striking example of multilayer-based strong iridescent coloration in plants, in the fruit of Pollia condensata. The color is caused by Bragg reflection of helicoidally stacked cellulose microfibrils that form multilayers in the cell walls of the epicarp. We demonstrate that animals and plants have convergently evolved multilayer-based photonic structures to generate colors using entirely distinct materials. The bright blue coloration of this fruit is more intense than that of any previously described biological material. Uniquely in nature, the reflected color differs from cell to cell, as the layer thicknesses in the multilayer stack vary, giving the fruit a striking pixelated or pointillist appearance. Because the multilayers form with both helicoidicities, optical characterization reveals that the reflected light from every epidermal cell is polarized circularly either to the left or to the right, a feature that has never previously been observed in a single tissue.

A third species of Polyspatha, an Africanendemic genus of Commelinaceae.

Polyspatha oligospatha Faden, the third species in a small African endemic genus of Commelinaceae, is described. It is widespread but has been overlooked because of its small stature and resemblance to small plants of Polyspatha paniculata. It differs from both Polyspatha paniculata and Polyspatha hirsuta, the two other species, by its leaf pubescence, fewer, more widely spaced and usually patent spathes, deeply ridged seeds with numerous knobby, transversely interrupted ridges, and morning anthesis. It occurs throughout the Congolian forests from Cameroon to Uganda, but it is also disjunct in Ivory Coast, across the Dahomey gap.

Floral organogenesis and the developmental basis for pollinator deception in the asiatic dayflower, Commelina communis (Commelinaceae).

The upper half of flowers in Commelina communis deceptively lures potential pollinators with its showy petals and staminodes on the false promise of abundant pollen. This paper presents evidence that staminodization in the upper half is associated with a severe retardation of the entire upper floral hemisphere early in development. Possible consequences of this developmental retardation are seen also in the gynoecium, where the upper carpel of the three-carpellate ovary is underdeveloped and sterile at maturity. Only late in development do the upper petals and staminodes expand and acquire pigments necessary for their attractive function. We surmise that retardations of this severity are unlikely to be found for functionally fertile organs such as stamens and ovule-producing carpels, because key preparatory events preceding sporogenesis might otherwise be disrupted. Such differential growth about the floral apex resembles that known in some eudicots to be regulated by the TCP gene family; thus, future molecular developmental studies in Commelina may help to extend our understanding of the evolutionary genetics of floral monosymmetry to monocots.