Family: Campanulaceae

Class: Angiospermae (dicotyledons)
Order:
Asterales
Common names:
bell flower, bluebell family (Eng.); klokkiesfamilie (Afr.)

Roella cliata

This is a cosmopolitan family with showy flowers, mainly from the northern hemisphere, but in the southern hemisphere South Africa is particularly rich in members of this family.

Description
In South Africa the family contains mostly herbs (annual, or perennial) or rarely small shrubs. The leaves are alternate, rarely opposite, simple, and without stipules. The flowers are regular, bell-shaped, funnel-form or salver-form (corolla with a narrow tube and small spreading lobes) and bisexual. They are borne singly or more often in inflorescences. The large, showy flowers are predominantly blue in colour. Petals, sepals and stamens are normally in fives. The petals are partially or completely fused and are inserted on an inferior or half inferior or seldomly a superior ovary. There are as many stamens as corolla lobes. The style is simple with as many stigmas as carpels. The fruit is a capsule.


Wahlenbergia procumbens


Roella amplexicaulis

Roella cuspidata

 

Distribution
The Campanulaceae has a cosmopolitan distribution, although more abundant in temperate and subtropical regions and consists of about 55 genera and more than 900 species. In South Africa there are 10 genera of which eight are endemic and about 250 species. Some of the genera are discussed below.

The largest and most widespread genus is Wahlenbergia, which comprises 170 species. W. capensis is a common blue-flowered spring annual that is often found along roadsides and on open fields around Cape Town. Most of the annual species occur on the West Coast and in the Northern Cape in sandy soil in open vegetation. Recently all 46 species of the shrubby genus Lightfootia have been placed in Wahlenbergia.

Roella ciiataRoella is a genus of small shrubs found mainly in the southwestern Cape. Only one of the twenty-four species extends into the Eastern Cape and KwaZulu-Natal. Plants grow mainly on stony mountain slopes. Its large blue flowers are borne on the tips of branches in groups or singly. The best known species in this genus is R. ciliata.

Rhigiophyllum squarrosum:Copyright W MM EddieRhigiophyllum is one of two genera consisting of only a single species. The other one is Treichelia. Rhigiophyllum squarrosum is a small shrub, which occurs only in the Napier-Bredasdorp area, whereas Treichelia longebracteata is an annual known from a few localities in the Cape Peninsula and one in Hermanus.


Name and History
The regular and irregular flower shapes of members of the Campanulaceae has always been the subject of dispute and uncertainty. Some taxonomists prefer to consider the Campanulaceae as one complex, variable family with several subfamilies. New evidence from morphology and DNA sequence data has contributed to the current recognition of five subfamilies within the Campanulaceae: Campanuloideae, Lobelioideae, Cyphiodeae, Cyphocarpoideae and Nemacladiodeae. Only the Campanuloideae, Lobelioideae and Cyphiodeae are represented in South Africa, the other two subfamilies occurring in Chile, southwestern United States and northwestern Mexico. For the purpose of this article, I consider the Campanulaceae in the strict sense, that is, not recognizing subfamilies, instead recognizing the families Campanulaceae, Lobeliaceae and Cyphiaceae.

Ecology
Merciera azureaMany of shrubby members of the family occurring in the fire-prone fynbos vegetation of the southwestern Cape, resprout after fire. Plants in the genus Merciera grow and flower most profusely in recently burnt veld. After six years, the plants start to die and start disappearing when the veld remains unburnt for very long periods. Plants in the dry parts of the country have adapted to long periods of drought by developing an annual life cycle.

An interesting mechanism has been developed in the family to facilitate cross-pollination and hinder self-pollination. The flowers are distinctly protandrous (male reproductive organs mature first), and pollen is shed upon the style (with the stigma lobes closed up against one another) in the bud. The style is either sticky or hairy, to hold the pollen. This is the male stage in the development of the flower and stamens wilt quickly as the corolla opens. After a time when the bulk of the pollen has been carried away by insects, the stigma lobes unfold and the female stage sets in. The stigma is now ready to receive pollen from another plant.

Economic and cultural value
Species of the genera such as Wahlenbergia, Campanula, Symphyandra, Jasione and Phyteuma are popular garden ornamentals. Only Wahlenbergia occurs in South Africa. Occasionally Roella ciliata is planted as a garden ornamental.

I know no cultural usage of members of the family.

In the Garden
Wahlenbergia undulata and W. rivularis are popular garden plants.

References and further reading

Cupido, C.N. & Conrad, F. 1999. Bellflowers. Veld & Flora 85: 180-181
Kovanda, M. 1978. Campanulaceae. In V.H. Heywood, Flowering plants of the world: 254-256. Oxford University Press, Oxford.
Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
Van der Walt, L. 2001-01. Wahlenbergia undulata (L.f.) A.DC. (Campanulaceae) on www.plantzafrica.com

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Chris Cupido
Compton Herbarium, Kirstenbosch
September 2004

 


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