104 THE STORY OF PLANT LIFE 



types of habitat. They are found in all parts of the 

 world, chiefly in the temperate regions, often at high 

 altitudes, some being arctic alpine. A few, as some 

 of the Centauries, are halophytes. The Bogbean is 

 a marsh plant. The Gentians are moorland or heath 

 plants. Gentiana prostrata grows at 6000-9000 ft. in 

 Europe, in the Rocky Mountains at 16,000 ft., whilst 

 at the Behring Straits, it is found at or near sea 

 level. The colours of the flowers of species found in 

 Europe are blue, whilst in S. America and New 

 Zealand the flowers are red. Only a few are yellow, 

 e.g. Chlora, or white {e.g. Bogbean). 



A few of these plants are shrubby, but most of them 

 are perennial, herbaceous types, with rhizomes. 

 Some of the Gentians are annual. The leaves are 

 usually entire, opposite, without stipules. In the 

 Bogbean they are trifoliate. Rarely the leaves are in 

 whorls. In Limnanthemurn the leaves are floating 

 and alternate. 



The inflorescence is cymose, terminal or panicled, 

 dichotomous. There is only one flower in each fork. 

 The flowers are regular, solitary, with the parts in 

 fours or fives. They possess bracts and bracteoles, 

 or not. The calyx is gamosepalous, inferior, persis- 

 tent, with usually five lobes, or four to eight, overlap- 

 ping in bud. The regular corolla is hypogynous, mono- 

 petalous, with four petals united below, or four to eight 

 lobes, and is bell-shaped or funnel-shaped, wheel- 

 shaped, or salver-shaped, twisted in bud, sometimes 

 persistent. The tube is straight or open, often short, 



