Taxonomy of Flowering Plants - LECTURE NOTES - Spring, 1998
Hugh D. Wilson - rm. 306, Butler Hall
23 March 1998
The Rosidae
Family Overview - The Rosales

Crassulaceae - the Stonecrop Family

Diversity:  A family of 25 genera and over 900 species of  annual and perennial (mostly) herbs and some shrubs.  Mostly xerophytes that sequester water in the leaves producing a fleshy leaf succulence, manifested by many 'rock garden' taxa in this family.  Many genera also show an unusual (present in about 5% of the flowering plant species - ca. 18 families) physiological feature, "Crassulacean acid metabolism (CAM)", that allows gas exchange (CO2 acquisition and conversion to organic acids) to occur at night, via open stomata (pores in the leaves) and, during the day when the stomata are closed, the CO2  released and used immediately in photosynthesis. As a result, the plant is able to conserve water.

Distribution:  World wide, but most diverse in southern Africa - we have 5 genera witrh 11 species in Texas.

Floral structure:

 
 Significant features:  Vegetative characters include fleshy, succulent leaves that often show a three-dimensional (as opposed to laminar) form, either opposite or alternate.  Generic variation with regard to perianth part numbers and connation; stamens usually twice the number of perianth parts, and the gynoecium usually apocarpous (some basal fusion) with each carpel subtended by a nectar-producing scale and the fruit a follicle
 
 
   Sedum nuttallianum  - rare local (sandy areas) of the largest Genus.

  Sedum nuttallianum - succulent leaves, sepals - and apocarpy

 
4-merous, connate flower (left) and inflorescence (right - UH Botany) of Kalanchoe
 
More information on the Crassulaceae

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