The tracheid bar, a strip composed of vertically oriented large tracheid-like cells (tracheoids), occurs only in the hilum of seeds of papilionoid legumes. An anatomical survey of the bar was made from seeds representing 232 species of 97 genera from 29 of the 31 tribes recognized by Polhill. Seeds were sectioned freehand, coated, then viewed by SEM. The tracheid bar is quite uniform in its general features throughout the subfamily, although differences in size and shape of both the bar and the tracheoids were found. Eight species from tribes considered to be among the primitive elements of the subfamily exhibited three variant forms: horizontal tracheary elements instead of the usual bar (2 species), tracheid bar with subtending but separate vascular bundle (1 species), and the tracheid bar with fused horizontal tracheary elements (5 species). Bordered pits of individual cells in the tracheid bar virtually always lacked a membrane and had smooth, warty, or variously elaborate vestures on the border. This appears to be the first report of vestured pits other than in secondary xylem. With some exceptions, bordered pits tended to be vestured in primitive tribes, warty in intermediate tribes, and smooth or only slightly warty in the most advanced tribes. A TRACHEID BAR occurs only in papilionoid legume seeds. It is a strip of large tracheid-like cells (tracheoids) which are lignified, pitted, and almost always oriented with their long axis perpendicular to the hilar groove. The tracheid bar extends from the micropyle at one edge of the hilum to the ovular bundle which enters the seed at the opposite edge (Fig. 1). These facts were known in the 19th century (Mattirolo and Buscalioni, 1892; Pfaefflin, 1897; Pammel, 1899), although based on a small number of taxa. In this century, numerous light microscope investigations have depicted the hilum only in transectional view, and without much detail of

Tracheid bar and vestured pits in legume seeds (leguminosae: papilionoideae)

Development and structure of seeds in some Genisteae (Papilionoideae-Leguminosae)

The diversity of vascular patterns in flowers of Fabaceae subfamily Faboideae is outstanding yet remains relatively overlooked. Studies of floral vasculature are fairly scarce, and the phylogenetic framework they have been interpreted in is outdated. Here we propose a reassessment of previous results, underlining the relevance of vascular characters for systematic studies. A thorough literature survey was conducted, we bring some remarkable and seminal work from the late 1960s into light, and we include recent results leading to the description of an until now unrecognized floral vascular pattern in Faboideae. Our review shows that the high diversity of floral vasculature patterns among Faboideae is mostly due to the shape and number of traces, the vertical and horizontal fusions among bundles, and the mode of division of stamen traces. The distribution of the different vascular patterns in the phylogeny of the subfamily does not seem random, particularly at the tribal level. In addition, floral nectaries located between the stamens and the carpel exhibit contrasting vascular supplies in Faboideae. Morphological constraints might have an impact on the division mode of the traces of Faboideae flowers with numerous stamens. Our review provides groundwork for future studies aiming to clarify the nature of floral nectaries’ structure and further investigate the evolution of floral vascular patterns in Faboideae using a representative taxonomic sampling and an updated phylogenetic framework.

What Is inside a Papilionoid Flower? II. Insights into the Vascular Anatomy of Faboideae

Premise of research. The diversity of vascular patterns in flowers of Fabaceae subfamily Faboideae is remarkable yet remains somewhat overlooked. Here we propose an empirical examination of anatomical features of flowers of a selected group of Faboideae in which taxonomic delineation is currently being investigated in order to reassess the relevance of floral vascular characters for systematic studies. We focus on the New Caledonian endemic clade Arthroclianthus-Nephrodesmus, exhibiting contrasting flower morphologies. Methodology. Preanthetic floral buds of 6 of 17 species of the genera Arthroclianthus and Nephrodesmus were selected from herbarium specimens and a living tree. They were cut in serial transverse sections and studied with light microscopy. Pivotal results. We identify three vascular organizations in the Arthroclianthus-Nephrodesmus clade: the N. francii, A. sanguineus, and A. microbotrys patterns. The N. francii and A. sanguineus patterns both belong to the unihiate series. In the A. sanguineus and A. microbotrys patterns, the receptacle is vascularized by a similar number of traces, higher than in the N. francii pattern. We describe a very rare Faboideae vascular organization in A. microbotrys, the unihiate-dihiate series. Conclusions. The diversity of floral vascular anatomies shown by the Arthroclianthus-Nephrodesmus clade is the greatest among the 80 studied genera of Faboideae. Our results do not support the conservation of the current delineation of the two genera and are consistent with ongoing molecular investigations. The size of the flower organs could constrain vascular organization of the flowers, explaining the differences in the number of traces in the receptacle.

What Is inside a Papilionoid Flower? I. Floral Vascular Anatomy in the New Caledonian Endemic Clade Arthroclianthus-Nephrodesmus (Fabaceae, Faboideae)

Seed morphology, seed coat development and structure have been studied inCrotalaria burhia Buch-Ham.,C. medicaginea Lamk.,Tephrosia hamiltonii Drumm. andT. apollinea Link. Seed coat is formed by the outer integument alone. Inner integument plays no role in its formation and degenerates. InTephrosia species, the inner layer of inner integument acts as an integumentary tapetum. The nucellus persists for a long time at the chalazal end in the form of nucellar pad in both of theTephrosia species.

Structure and development of seed coat inCrotalaria andTephrosia species

InCrotalaria burhia Buch-Ham.,C medicaginea Lamk.Tephrosia hamiltonii Drumm. andT. apollinea Link studied here, the floral organs develop in an acropetal sequence and are not congenitally fused. Calyx and staminal tubes are formed due to zonal intercalary growth at their bases. Floral anatomy conforms to dihiate series inCrotalaria species with two sets of gaps and to unihiate series with single set of gaps inTephrosia species. InTephrosia species there is a glandular disc present on the inner side at the base of stamens which is vascularized by the staminal traces. InCrotalaria species, no prominent disc is present but some densely cytoplasmic cells lining the receptacular cup are clearly discernible which are nonvascularized. Mucilage cells have been observed in the floral parts inTephrosia species. The mucilaginous cells are multinucleate, formed by the dissolution of cell walls of the surrounding cells.

Arvinder Kaur Narang

Papers

Structure and development of seed coat inCrotalaria andTephrosia species

Anatomical studies inCrotalaria andTephrosia species. Vasculature of flower