THE DICOTYLEDONES 



1781 



America. They are distinguished from the Myrtaceae by the absence of oil 

 glands and by the fact that the anthers dehisce by apical pores. There are 

 three prominent longitudinal veins on the leaves connected by pinnate 

 side branches, a vegetative feature which is strikingly characteristic of the 

 family. Bicollateral and concentric, cortical, and medullary vascular 

 bundles occur. Many species are cultivated on account of their flowers, 

 particularly the genera Medinilla and Centradenia which are common 

 greenhouse plants. None has any great economic importance. 



Onagraceae (Oenotheraceae) 



This family, which is sometimes called the Oenotheraceae, is represented 

 in the British Flora mainly by the Willow-herbs but several well-known 

 cultivated plants also belong to the family, among which we may mention 

 Fuchsia, Clarkia and Godetia. Among the common British species are 

 Epilobium angustifoUum (Rose-bay Willow-herb), E. hirsutum (Hairy Willow- 

 herb), and E. parvifloriim (Hoary Willow-herb), Oenothera biennis (Evening 

 Primrose) and Circaea lutetiana (Enchanter's Nightshade). 



The plants are mostly herbaceous with alternate or opposite leaves and 

 axillary or terminal racemose inflorescences. Many are annuals, others 

 biennials, while the family also includes certain shrubby genera such as 

 Fuchsia. 



The flowers (Fig. 1673) are hermaphrodite, actinomorphic or occa- 

 sionally zygomorphic, tetramerous or occasionally dimerous and epigynous. 



Fig. 1673. — Floral diagram of 

 Epilobium hirsutum. Ona- 

 graceae. 



The calyx is composed of two or four sepals, superior and sometimes 

 petaloid as in Fuchsia. 



The corolla is composed of two or four petals or is occasionally absent. 

 The petals may be contort or imbricate. 



The androecium consists of as many or twice as many stamens as 

 there are sepals, the anthers are two-chambered and open lengthwise. The 



