Angiosperms of Senegal: Key to the families of the class dicotyledons

The Angiosperms are the best known and most diversified group in Senegal. However, even if a lot of work has been done on this group, more needs to be done. The main objective of this work is to contribute to a better knowledge of the biodiversity of dicotyledons in Senegal. More specifically, this work seeks to propose a determination key for the families of dicotyledons in order to facilitate their identification. Based on bibliographical research, a rough table and a summary table listing the different characters of the vegetative and reproductive systems of the families of the Dicotyledons of Senegal have been drawn up. These tables were used to propose dichotomous keys. This work made it possible to propose determination keys essentially based on the stable characters of the vegetative and reproductive systems of these families.


Introduction
In the flora of Senegal, Angiosperms constitute the most diverse group. Previous studies [2] have shown that Dicotyledons are largely more represented than Monocotyledons in Senegal. Thus, in this West African country, flowering plants, which are relatively well known, comprise about 2500 species [13]; [2].
However, even if most of the flora is known, some geographical areas remain to be surveyed. However, in West Africa, the identification of plant species presents particular difficulties as floras are often lacking. In addition, the plants do not flower synchronously and the collected material is often sterile, which makes a complete determination of the specific alpha-diversity almost impossible during a short mission [20]. Thus, in poorly surveyed areas, only a family specialist can guarantee an accurate determination of the species [20]. Indeed, the main work of the botanist in the field is to identify the material up to the family level, as specialists generally work at this level and it is to them that the material should be sent for a definitive determination [20]. In the case of Senegal, although Berhaut [4] proposed a species determination key, a family key is not yet available. The main objective of this work is to contribute to a better knowledge of the biodiversity of Senegal. More specifically, this work seeks to propose a determination key for families belonging to the class of dicotyledons. 7' -base of petiole not sheathing 8 -seeds capped with a tuft of hairs; trees, shrubs or herbs, often lianas; trunk sympodial and branches whorled; stem growth bayoneted visible on young trees; shrubs sometimes candelabra-shaped; latex white abundant at the notch; leaves opposite, or alternate, sometimes condensed into flecks, simple, entire ; sometimes glandular stipular appendages; inflorescence axillary or terminal, cymeous, racemose or solitary flower; corolla with twisted preflowering; stamens alternately fused to corolla; ovary sterile to semi-infertile; fruit a more or less elongated follicle, or a berry.
15 -inflorescence in a simple or more or less branched axillary spike; perennial, herbaceous, fleshy, voluble or trailing, may be green or red; leaves alternate, glabrous, semi-fleshy; blade oval, rounded wedge-shaped at the apex, broadly rounded at the base, then abruptly and shortly wedge-shaped, leaving a more or less distinct stalk; three to five lateral veins, those at the apex not very sensitive; fruit, globose berries, usually black when ripe.

15' -inflorescence of different type
16 -plants with often jointed stems, sometimes climbing and with aerial roots, or stoloniferous; herbaceous perennials, more rarely shrubs; most species succulent, leaves alternate, simple, sometimes asymmetrical at base, with free stipules, deciduous; margins rather finely toothed, or with teeth interspersed with stronger teeth; flowers monoecious, actinomorphic, the males with two imbricated or absent sepals.

16' -plants with unjointed stems
17 -fairly thick, spongy, waterlogged stem; annual or perennial herbaceous; glabrous stem; leaves generally alternate, simple or lobed; leaves sometimes sessile; about ten fine veins running along the edges of the blade after leaving the median; the flowers, sometimes very conspicuous, are axillary or arranged in a cyme; the fruit is a capsule.

.Hydrophyllaceae
17' -stem normal in appearance, not spongy 18 -flowers tubular, irregular, often double-lipped; herbaceous, but sometimes also shrubs or even small trees; leaves usually alternate; calyx over ovary has 5 lobes; fruit is a capsule, sometimes a berry.

Conclusion
This study, whose aim was to contribute to a better knowledge of the plant biodiversity of Senegal, has shown that in the flora of Senegal, the dicotyledons are rich in 130 families. The families differ from each other by a certain number of characters elucidated in the determination keys. Indeed, this work has made it possible to propose two determination keys based on the distinctive characters of the vegetative, in particular the presence and absence of leaves, and reproductive systems of the families of the class Dicotyledons. Compliance with ethical standards.