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A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1537. — Kalanchce {Crassula) flammea. 

 Flowering shoot. 



number and free. The ovary is 

 either apocarpous or syncarpous and 

 the ovules are generally numerous 

 with axile placentation. The seeds 

 usually possess copious endosperm 

 and the embryo is straight. 



We shall consider the Saxifra- 

 gaceae in detail below, but before 

 doing so we must say something 

 about the important family Crassu- 

 laceae and refer more briefly to the 

 Cephalotaceae and Podostemaceae. 



The Crassulaceae are a large 

 family containing some twenty-five 

 genera and about 1,450 species, a 

 number of which occur in Britain. 

 They are mostly perennial plants 

 living in dry situations, especially 

 in South Africa. The plants are 

 usually xerophytes, generally show- 

 ing succulent characters, with fleshy leaves and sometimes with contracted 

 stems. Many exhibit vigorous vegetative propagation by means of rhizomes 

 or oflFsets. Some, such as Crassula (Fig. 1537), form bulbils, others, such 

 as Bryophvlhiin, produce new plants from buds borne on the leaves. The 

 anatomy of the leaves usually 

 shows a large development of 

 parenchyma and a small de- 

 velopment of vascular tissue. 

 Mucilage cells are generally 

 present. 



The flowers are usually 

 borne on long fleshy stems, the 

 inflorescence being a cincinnus, 

 as in Echeveria (Fig. 1538). 

 The flowers are usually herm- 

 aphrodite, actinomorphic and 

 very regular in construction, 

 the number of parts varying 

 from three to thirty. The family 

 is exceptional in having the 

 petals more or less united into a 

 corolla tube in certain genera, 

 e.g., Bryophylliim, Cotyledon, 

 Rochea, etc., a feature which 

 is rare in the Archichlamydeae. 

 There are usually twice as many Fig. 1^3^.— Echeveria elegans. Inflorescence. 



