THALAMIFLOR^ 125 



next flower. Usually bees pollinate them. Except 

 in the Pansies the showy spring flowers do not set 

 seed, but the autumn closed flowers, termed cleisto- 

 gamic, and bud-Hke, do so, the flower being in this 

 case self-pollinated. 



The valves of the capsule contract and the seeds 

 are jerked out to a distance. The Violets and Pansies 

 are favourite garden flowers. Ipecacuanha is derived 

 from the Violet. 



10. The Sea Heath Group. 



There are two plants in the British Flora belonging 

 to the order Frankeniaceae, of which the commoner 

 one is selected as a type. 



They are maritime plants or halophytes, distributed 

 over North Africa and South Europe, adapted to 

 what is termed physiological drought, or a condition 

 in which the soil-water is inimical in great quantities 

 to the well-being of the plant owing to the super- 

 abundance of mineral salts. A similar state of 

 things is characteristic of moors and bogs, where the 

 peaty soil is similarly charged with humous acids, 

 which affect and reduce absorption, and therefore 

 the plants must adapt themselves so that transpira- 

 tion is not in excess of absorption. This is achieved 

 by a reduction in leaf surface, and by other means, 

 and the effect of heat is counteracted by the provision 

 of a coat of wax, overlapping leaves, a covering of 

 hairs, etc. Physical drought, on the other hand, is 

 directly due to a lack of water in the soil. 



