1936 A TEXTBOOK OF THEORETICAL BOTANY 



extend their range to temperate regions while a few are found under sub- 

 Arctic conditions. The flowers of the Rubiaceae are hermaphrodite, 

 usually actinomorphic and either tetramerous or pentamerous, with five 

 or four stamens and two carpels. The corolla is tubular and the stamens 

 are inserted on the corolla tube, the anthers being introrse and bilocular. 

 The ovary is covered by a fleshy disc, is usually inferior and contains 

 usually two loculi with one to many anatropous ovules. The fruit is a 

 capsule, drupe or berry; the seeds have a straight embryo lying in carti- 

 laginous or horny endosperm. They are mostly shrubs or trees but those 

 occurring in Britain are herbs. These herbaceous types all belong to a 

 single tribe, the Galieae, which occupy a somewhat anomalous position 

 within the family. In this tribe the stipules are leaflike and are grouped 

 with the true leaves into whorls on the stem, distinguishable from the 

 leaves by having no buds in their axils. Species of Galium (Fig. 1863) 

 (Bedstraw) are common in Britain, G. aparine (Cleavers) being well known 



Fig. 1863. — Galium erectum. Paniculate inflorescence of small, 



white flowers. 



as a scrambler, climbing by stiflt recurved hairs. Among the other genera 

 included in this tribe are Asperula (Woodruff), Sherardia, Crucianella 

 (see Fig. 1254) and Riihia. Riibia tinctoria (Madder) contains the dyes 

 alizarin and purpurin in the roots, for which it was formerly cultivated in 

 India. 



One of the most important genera belonging to the family is Cojfea 

 (Fig. 1864) which contains forty-five species especially common in Africa. 

 C. arabicUy Arabian coffee, is now largely cultivated in Brazil, Java and the 



