24 THE STORY OF PLANT LIFE 



are twining plants, as Dodder, root-climbers, as Ivy, 

 and there are also hook-climbers, tendril-bearers, and 

 leaf-climbers. 



Amongst the autonomous plants are renascent 

 herbaceous plants including those with tufted 

 rhizomes, as Columbine, or crown formers, mat- 

 geophytes with tubers, bulbs, etc., e.g. Crocus, 

 travelling geophytes with spreading rhizomes, etc., 

 as sedges. Rosette plants form a rosette of radical 

 leaves, as the Plantain. There are also creeping 

 plants with rooting stolons as many heath plants, 

 e.g. Whortleberry. 



Plants with erect perennial shoots include cushion 

 plants such as Stonecrops ; and there are other types 

 such as undershrubs, e.g. bramble, soft-stemmed 

 plants, e.g. Lords-and-Ladies, succulents, as Sun 

 Spurge, woody plants, e.g. canopy plants, trees, 

 shrubs and dwarf shrubs. 



The form of the different parts of plants is largely 

 due to adaptation to function or to factors of 

 environment."^ 



Roots serve for absorption and are adapted to this 

 end. Their forms vary according to the soil or the 

 water content. Roots serve also as a means of 

 attachment.! There is a primary root and a secon- 

 dary root. The latter are lateral, and produce tertiary 



* Functional needs, however, also demand variation in internal 

 structure, 



t And are modified, therefore, to meet the requirements of each 

 type of habitat. Terrestrial and aquatic plants differ markedly for 

 this reason in form as in function. 



