MODES OF GROWTH 115 



2. Plants with Radical Leaves only : 



(a) Rosette-plants e.g., dandelion. The daisy is really 

 a cushion-plant, but the stems have sunk below the level 

 of the ground, producing on the surface a number of 

 distinct rosettes. 



(6) Some bulbous geophytes e.g., crocus, wild hya- 

 cinth. 



3. Plants with both Radical and Cauline Leaves : 



(a) Most biennials. 



(b) Some herbaceous perennials e.g., oxtongue (Hel- 

 minthia echioides), rock-cress (Ardbis), and some hawk- 

 weeds. 



(c) Grass-like plants with tufted habit e.g., tussock- 

 grasses, like Air a flexuosa and Holcus laiwtus, and some 

 sedges. 



II. Epiphytic Plants, perched on Trees (see p. 121). 



Except in geophytes, these differences of habit are due 

 to the many and varied methods adopted by plants to 

 secure for themselves an adequate amount of sunlight. 

 Leaves, as the chief assimilating organs, seek to take the 

 most favourable light - position. Trees effect this by 

 lifting up, on tall trunks, a crown of foliage above the 

 surrounding vegetation. Plants with prostrate trailing 

 stems thread their devious ways among the lower vegeta- 

 tion, seeking out favourable spots where their leaves may 

 catch the light. The creeping habit of long frail stems 

 leads to the scrambling habit, in which the stems hook 

 and catch on to other plants, scrambling over their backs 

 into the light. From the scrambler to the climber is a 

 short step. Epiphytes make their light-position secure 

 by perching on the elevated branches of trees. 



Climbing Plants. These have long weak stems, and 

 solve the problem of reaching a position of advantage by 

 climbing up the bodies of other plants. They derive no 

 nourishment from the supports upon which they lean, 

 although occasionally they injure them by intercepting 

 the light which properly belongs to them. Climbing 

 plants were divided by Charles Darwin into the following 

 groups : 



1. Scramblers, or Hook-Climbers. These are the least 

 specialized of climbing plants, and are not far removed 



