1700 A TEXTBOOK OF THEORETICAL BOTANY 



tropical herbaceous plants related to the last order through the Passi- 

 floraceae and Caricaceae. Many of them are climbers attaching themselves 

 by tendrils. 



The most important family is the Cucurbitaceae which includes about 

 ninety genera and 750 species. They are mostly annual or occasionally 

 perennial herbs bearing large unisexual flowers. Many are of economic 

 importance, e.g., Ciiciirhita pepo, the Pumpkin or Vegetable Marrow; 

 Cucumis tnelo, the Melon; C. sativus (Fig. 1564), the Cucumber; Citrullus 



Fig. 1564. — Cucumis sativus. Flowering shoot 

 with tendril. 



vulgaris, the Water Melon. Also included in this family is EcbaUium 

 elaterium, the Squirting Cucumber (see Fig. 1382). Bryonia dioica (White 

 Bryony) is the only British example. 



A second family, the Begoniaceae, may be noted because of the 

 important genus Begonia, many species of which are commonly cultivated. 

 The flowers are unisexual (Fig. 1565). Many show remarkable powers of 

 vegetative propagation by means of buds formed on detached leaves. They 

 are mainly tropical in distribution. 



Another order, the Guttiferales, was included by Engler in his Parietales, 

 but is now generally separated on account of the axile placentation of the 

 ovules. The order includes a number of not very large families mostly not 

 represented in the British Flora. Certain species however are of economic 

 importance. 



The most important family is the Theaceae, which includes the genus 

 Camellia. C. sinensis (Fig. 1566) is the tea plant, an erect, bushy shrub 

 with smooth, leathery, oval leaves. The flowers are white and scented. It 

 has been cultivated from very early times (probably before the sixth 



