150 THE STORY OF PLANT LIFE 



The seeds are eight to twelve, straight, ascending, 

 numerous, ribbed and furrowed transversely. 



The flowers open between July and September. 

 The plant is a herbaceous annual. It is a creeping 

 plant. 



As an aquatic plant with flowers frequently sub- 

 merged, the flowers are probably largely cleistogamic, 

 being small and axillary. 



The capsule opens when ripe, and the seeds are 

 dispersed in the water. 



The plant has acrid properties. 



Elatine hexandra. — The habit of Waterwort is 

 well shown in the illustration, Fig. 28, the plant being 

 aquatic, and more or less streaming in habit. Fruit is 

 shown in the centre. 



15. The St. John's Wort Group. 



The order Hypericacese has been placed by 

 Engler in the Guttiferse, including a few foreign 

 types, with about four hundred and fifty species and 

 forty-two genera. They are mainly tropical, and 

 these embrace types which differ in the number of 

 parts in the flower, the arrangement of stamens, or 

 the seeds. Some of these are tall shrubs or trees. 

 In the order Hypericacese the numerous stamens in 

 three or five bundles are a characteristic feature. 



In Britain the only representative is the genus 

 Hypericum, found in South Europe, West Asia, and 

 North America. 



