212 THE STORY OF PLANT LIFE 



RuMEX CRispus. — In Fig. 6i the root-stock is shown 

 with a radical leaf, curled at the edge and crisped, with 

 a long petiole. The upper leaves become bract-like in the 

 panicle. The flowers are in whorls. 



63. The Birthwort Group. 



Only two types of the Order Aristolochiaceae are 

 represented in the British flora. There are, how- 

 ever, some two hundred species, included in five 

 genera, which are mainly natives of the Tropics or 

 Warm Temperate regions. They are not, however, 

 found in the Australian region. Asarabacca and 

 Aristolochia or Birthwort are the British types. In 

 the former the perianth is tubular, curved, with an 

 oblique entire Hmb. The Dutchman's Pipe is often 

 found in gardens. 



The relationship between this order and others is 

 not clear. The group may, however, be compared 

 with the Nepenthaceae and Rafflesiaceae. 



These plants are mainly herbs or shrubs. Some 

 are climbing plants, or twining lianes. The leaves 

 are alternate, stalked, simple, entire or lobed, heart- 

 shaped. There are no stipules. 



The flowers are hermaphrodite, regular, or zygo- 

 morphic, epigynous, brown or green, solitary, or in 

 racemes. The perianth is superior, tubular, bell- 

 shaped or trumpet-shaped, petaloid, with the Hmb 

 three-lobed, or one-lipped, or entire, valvate in bud. 

 The stamens are six to thirty-six, free or united with 

 the style, epigynous. The anthers are nearly stalkless. 



