CHAPTER VIII. 



CLIMBERS, PARASITES, SAPROPHYTES. 



227. Climbing Plants. Many plants have special means 

 of growing up towards the light and air, and thus placing 

 their leaves, flowers, and fruits in a favourable position, with 

 the least expenditure of material. They are weak- stemmed 

 plants which make use of living or dead plants as supports, 

 without whose aid they would, after reaching a certain height 

 by their own efforts, sink to the ground. Climbing plants 

 save themselves the expense of forming rigid stems, but 

 with a few exceptions (of which the Dodder is the only 

 British example) they are not parasites, since they have 

 earth-roots and take nothing from the plants to which they 

 attach themselves, though when climbing over living plants 

 they may injure them indirectly by shading them from the 

 light. 



The chief methods employed by climbers to raise them- 

 selves are: (1) by twining their stems round the support; 

 (2) by producing special attaching organs or tendrils ; (3) by 

 producing special attaching roots; (4) by producing curved 

 prickles which hook on to the support. 



228. Tendril Climbers. It is necessary to distinguish 

 sharply between plants which climb by twining their stems 

 around supports and those which have special lateral irrit- 

 able organs tendrils for this purpose. In a tendril-bearing 

 plant, the stem itself grows straight on, while the tendrils 

 differ entirely from twining stems in their mode of action. 

 The tendrils can attach themselves to a support placed in 

 any position, and can coil around these to right or left, 

 downwards or upwards, differing in these respects from 

 twining stems. 



A young tendril, as it arises from the bud, is coiled up 



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