THE DICOTYLEDONES 



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stamens as petals. The carpels are generally united at their bases and 

 nectaries are usually present. Each carpel contains numerous ovules. The 

 fruit is often an etaerio of follicles and contains many very small seeds. 

 These seeds are usually devoid of endosperm. Pollination is often effected 

 by flies, the flowers being mostly protandrous. Many of the plants are 

 cultivated and are commonly planted in dry walls and rock gardens. 

 Sempervhiim (Fig. 1539) is called the House Leek, because one species, 



Fig. 1539. — Sempervivum tectorum. House Leek. 

 Flowering plant with many rosettes growing 

 over a rock. 



S. tectorum, was once commonly planted on cottage roofs as a protection 

 against "thunderbolts". The plants are amazingly tenacious of life and 

 will grow even in a herbarium press. Some fifty species are known from 

 southern Europe and the Himalayas. Cotyledon umbilicus (Pennywort) is 

 common on old walls in the western parts of Britain, and the same is 

 true of a number of species of Sedum (Fig. 1540) of which S. acre (Biting 

 Stonecrop) is the most common in dry and exposed places. 



The family Cephalotaceae is monotypic, the only species being 



