2i8 THE STORY OF PLANT LIFE 



28. The Stonecrop Group. 



Of the order Crassulaceas there are some four 

 hundred and fifty species and fifteen genera. The 

 order includes Stonecrop, House-leek, Navelwort 

 amongst British plants. The members of the Stone- 

 crop group are found in all parts of the world, 

 especially in South Africa. 



Most of them are succulent, fleshy plants, which 

 are full of water, and adapted to dry conditions, 

 growing in crevices of rocks, or on ledges. They 

 have also a very characteristic habit, being cushion 

 plants, with a matlike or tufted habit, with leaves 

 and stems closely packed together. The surface is 

 often coated with wax, and the stomata are immersed 

 in the epidermis — further adaptations to dry con- 

 ditions. They are largely propagated vegetatively 

 by offsets, or by bulbils, or by adventitious buds on 

 the leaves. 



The Stonecrop group includes succulent herbs and 

 shrubs. The leaves are alternate or opposite, without 

 stipules. The stems are frequently glandular. 



The flowers are usually in terminal or axillary 

 cymes, regular, actinomorphic, and hermaphrodite, 

 but sometimes unisexual, with or without bracts. 

 The calyx is gamosepalous and inferior, with three 

 to five, or ten to twelve, or more sepals, which may 

 be distinct or united below. The calyx is persistent. 

 The petals are of the same number, and sometimes, 

 as in the Navel-wort, gamopetalous, usually poly- 



