FLORA OF TROPICAL AFRICA. 



Order XCVIII. ACANTHACE^. (By I. H. Burkill and 

 C. B. Clarke.) 



Flowers hermaphrodite, irregular. Calyx inferior, free ; segments 

 5 or 4, nearly separate or sometimes more or less united. Corolla 

 gamopetalous ; tube campanulate or linear ; limb 2-lipped, or 5-lobed, 

 more or less 1 -sided. Stamens on the corolla, 4 didynamous, or 2 (with 

 or without rudiments) ; anther-cells 2 or 1, at base rounded, acute, or 

 tailed, parallel at equal height, or one above the other more or less 

 oblique ; pollen ellipsoid (then usually ribbed or banded longitudinally), 

 or globose (then often honeycombed, reticulate or echinulate) ; equatorial 

 pores 2, 3, 6, closed by stopples, for protrusion of pollen- tubes. Ovary 

 superior, 2-celled ; ovules superimposed in 1-2 rows or solitary (2, col- 

 lateral in Thunhergia, Afromendoncia), anatropous or obscurely amphi- 

 tropous ; style long, simple, minutely 2-fid. Capsule loculicidal, often 

 elastically dehiscent (in Afromendoncia a drupe) ; seeds usually nearly as 

 many as ovules, held up on the thickened up-curved outgrowth of 

 the funicle, the retinaculum (except in the first 5 genera), compressed 

 laterally ; albumen (except in the Nelsoniece). — Herbs or shrubs, 1 or 



2 arborescent. Leaves opposite ; stipules 0. Inflorescence various, in 

 strobiliform spikes, or heads, or lateral or terminal clusters ; or flowers 

 solitary, panicled or axillary ; bracts large or small or 0. 



An Order consisting of 140 genera and 2000 species, abundant in the tropics, 

 frequent in temperate climates, absent from Alpine and Arctic regions. 



In the tribe RuelUe(e, there is frequently a large anterior bract to the sessile flower, 

 and 2 lateral bracteoles between this and the flower. In the Eujtuticiecc, it is fre- 

 quently so difficult to distinguish the bract from the bracteoles that little use is made 

 of the character for descriptive purposes. In several cases, as in Phaylopsis, there are 



3 flowers subsessile in the axil of each (apparent) bract ; in such a case in the present 

 work each flower is then considered to be strictly without bract or bracteole, and the 

 " bract " enclosing an inflorescence is termed frequently a floral leaf. 



This terminology is merely descriptive ; for it very frequently happens that a 

 minute shoot, sometimes bearing a flower, appears inside the lateral bracteole. Also 



