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CHAPTER XVI 



THE ROOTS OF WATER PLANTS 



THE roots of certain of the more specialised water plants, 

 are extremelv reduced or even in some cases entirely 

 absent, e.g. CeraPopkyllum, Aldnrcandia and Utrkularia. In 

 other instances, such as Nymphaea^ although the primary root 

 is very short-lived, a considerable system of adventitious roots 

 may be developed. As we shall show in Chapter xxi, among 

 aquatics, absorption bv the roots is by no means of such negli- 

 gible importance as some writers have suggested; but at the 

 same time, when plants rooted at the bottom of water are 

 compared with those terrestrial herbaceous plants which they 

 most closely resemble in size and habit, it becomes clear that, 

 in the roots of the water plants, the function of anchorage has 

 assumed a greater importance, while the function of absorption 

 is less pre-eminent. A firm hold in the mud, and erectness of 

 the flowering stem., are often a sine qua non for aquatics, and 

 their roots help in various wavs to bring this about. Some- 

 times we merelv get a richlv ramifvine root system, e.g. Ranun- 

 culus aquatilis'^. In other cases the type of arrangement of the 

 adventitious roots is such as to hold the stem in position. This 

 point is well illustrated in a description written more than 

 seventy years ag^o-, of a certain amphibious plant, Oenanthe 

 Phelhindrium. "The flowering stem is remarkably fistulose, 

 furnished under water with frequent joints, which become more 

 distant upwards: it attains its greatest thickness two or three 

 intemodes from the base, where it is often an inch or more in 

 diameter. From the joints proceed numerous whorled pecti- 

 nated fibres [adventitious roots], of which the lower ones are 

 as stout as the original fusiform root: these, descending in a 

 conical manner to the bottom of the water, form a beautiful 



1 Hochreutiner, G. (i896> ^ Coleman, W. H. (18+4;. 



