46 



BRITISH PLANTS 



a source of danger to xerophytes, their leaves are arranged 

 to avoid the effects of full illumination. This is accom- 

 plished in several ways : 



1. The Leaves are arranged in Close Ranks or Files 

 on the stems, so that they overlap and shade one another 

 e.g., clubmosses (Fig. 16), the evergreen Veronicas grown 

 in gardens. 



2. The Leaves turn their Edges instead of their Surfaces 

 to the Light. The Eucalyptus is a xerophyte. During 

 the early years of its life, when the plant is more or less 

 screened by the trees around, the stem produces horizontal, 

 unstalked leaves. Later on it bears long, narrow, sickle- 



FIG. 16. Lycopodium davatum (COMMON CLUBMOSS), WITH SMALL, 

 CROWDED LEAVES. (SLIGHTLY REDUCED.) 



shaped, stalked leaves, which hang pendant, with their 

 edges turned towards the sky. Cladodes and phyllodes 

 also are generally vertical. 



The same light-avoiding habit is met with even among 

 marsh-plants. The iris, for example, has long, upright, 

 strap-shaped leaves. Many reeds and sedges have 

 circular leaves which are erect. Thus plants which in 

 other respects appear to be hygrophytes, may, if their 

 leaves are long-lived, exhibit some xerophytic adaptations 

 for winter conditions. 



We reserve the consideration of the xerophytic charac- 

 ters associated with hibernating organs (seeds, buds, 

 bulbs, rhizomes, etc.) for Chapter VI. 



