1878 



A TEXTBOOK OF THEORETICAL BOTANY 



contact with the stigma, so that automatic self-polHnation regularly takes 

 place, and, since few insects visit the plant, this is probably the normal 

 method of pollination. In dull weather the flowers never open and self- 

 pollination takes place pseudo-cleistogamously. 



In the tribe Samoleae is the single genus Samoliis with nine species, of 

 which S. valerandi (Fig. 1787) is cosmopolitan in damp ground, often by 

 the seashore. The flowers are small and the ovary semi-inferior. Self- 

 pollination is almost inevitable, for the stigma and anthers develop at the 

 same level and at the same time. 



Fig. 1787. — Sanwlus valeramli. 

 Longitudinal section of 

 flower. 



OLEALES 



The Oleales are Metachlamydeae in which the flowers are hermaphrodite 

 or unisexual by reduction, regular and generally tetramerous, the petals 

 being either free or united into a tube. The stamens are often reduced to 

 two. The ovary is superior, composed of two united carpels, and forming 

 a bilocular structure, each loculus having one or two pendulous, or basally 

 attached, anatropous ovules. The ovules usually have only a single integu- 

 ment. The plants are mostly woody shrubs, with opposite, simple or 

 pinnate leaves, and have flowers in small racemes. 



The various systems of classification diflFer in their interpretation of the 

 limits of the order. Bentham and Hooker called the Oleales the Gentianales 

 and included in it the families Oleaceae, Loganiaceae, Gentianaceae, 

 Apocynaceae and Asclepiadaceae. Engler combined the same families 

 under a different order which he called the Contortae. Wettstein pointed 

 out that there are essential differences between the Oleaceae and the 

 remaining families; such as the placentation of the ovules, and the 



