278 PLANT-LIFE 



light and air. Where colonies of Coltsfoot or Butterbur 

 subsist, there is little chance for would-be competitors. 

 The large leaves of these plants place all beneath them 

 in deep shade, taking light and air to themselves, and 

 allowing none to plants which attempt to exist on the 

 same ground. There is little wonder that, when the 

 leaves of these successful warriors die down in late 

 autumn or early winter, we discover the ground they 

 had shaded to be almost clear of other vegetation. 



The Daisy plant, when it grows among herbage which 

 tends to overshadow it, and which it is not sufficiently 

 powerful to suffocate, " draws up " to the light, and 

 develops a larger leaf-surface. The Dandelion does 

 likewise, its leaves becoming much longer, more delicate, 

 and having a less indented margin than is the case when 

 the plant ^rows in the open, where it suffocates com- 

 petitors by laying its leaves flat on the ground. When 

 the Dandelion, in adaptation to its habitat, grows as a 

 flattened rosette, the leaves are deeply indented, which, 

 of course, reduces the transpiring surface, and at the 

 same time considerably reduces the possibility of one 

 leaf taking light from another. In fact, the Daisy and 

 Dandelion jproduce " leaf mosaics." A leaf mosaic is a 

 close-pattern leaf arrangement in which each leaf is 

 situated in such a relation to other leaves as not to 

 intercept the light and atmosphere demanded by its 

 fellows, and it is a common feature in the plant world. 

 It is conspicuous in rosette forms, as already indicated, 

 in the Ivy that creeps over the floor of a wood, or 

 climbs up a tree-trunk, and in the leaves that are 

 massed at the ends of Sycamore branches. 



In relation to the need for light and air, plants have 



