Global description
Euphorbia convolvuloides is an erect plant with white latex. It has simple leaves, opposite and subsessile. It is reddish and covered with a denser pinkish-white hairs felting on the young organs. The inflorescences are grouped into lateral glomeruli. The cup is lined with 4 glands; it is strongly pubescent, as is the ovary.
Cotyledons
The cotyledons are elliptical and subsessile. They are 4 to 5 mm long and 1 to 2 mm wide. They are located between 5 and 10 mm from the ground surface. Immediately above them is the first pair of leaves.
First leaves
The first leaves are opposite, subsessile. The blade is lanceolate, marginally toothed. The second pair of leaves develops only 3 to 5 cm above the first. The stem and young leaves are tomentose.
General habit
Euphorbia convolvuloides is an erect plant. The top of the twigs is usually drooping. It develops in simple or very little branched axis, above the first pair of leaves. It measures 10 to 40 cm in height.
Underground system
The root is a taproot with fine rootlets. It pours a white latex when cut.
Stem
The stem is hollow and cylindrical. A white latex comes out when it is cut. It is reddish and covered with a white pubescence, dense and smooth, especially in young parts.
Leaf
The leaves are simple and opposite. They are sessile to very briefly petiolate and present on both sides of the petiole filiform stipules extremely reduced. They are 20 to 40 mm long and 6 to 13 mm wide. The limb is oval to lanceolate. The base is slightly asymmetrical and the margin is finely toothed. The lower and upper faces are finely tomentose. In young leaves undergoing elongation, this tomentum is dense and pinkish-white in color.
Flower
The flowers are assembled in cups (cyathium). Each cup contains a female flower reduced to a long-pedicelled 3-celled ovary, hanging on the outside and several male flowers reduced to a stamen, not exceeding the edge of the cup. These cupules are themselves grouped in glomeruli, on leafy side branches, very short. The cups are obconic in shape and have 4 purple glands with a white margin on the edge. The outer surface of the cup and the ovary are densely tomentose.
Fruit
The fruit is a dehiscent capsule with 3 cells, globular form. It measures 2 mm in diameter. Each lodge contains a single seed.
Seed
The seeds are polygonal, slightly arched longitudinally and are 1.5 mm long. They are covered with 4 or 5 deep horizontal grooves. They are orange-pink in color.