[ 195 J 



CHAPTER XV 



LAND FORMS OF WATER PLANTS, AND THE 

 EFFECT OF WATER UPON LAND PLANTS 



THE majority of water plants, with the exception of those 

 most highly specialised for aquatic life, are capable of 

 giving rise to land forms. Those plants which, when mature, 

 produce floating or air leaves, can obviously develop a land form 

 with less change in their structure and mode of life than those 

 which normally live entirely submerged. Limnanthemum nym- 

 phoides^) for instance, has been found growing on damp ground 

 with abbreviated internodes and petioles, and with reduced 

 laminae. Land forms ofHydrocharis*, and many Nymphaeaceae 3 

 and Alismaceae 4 are known, either in nature or in cultivation. 

 Successful terrestrial forms can also be produced by those 

 Potamogetons which possess coriaceous, floating leaves, or have 

 the power to develop such leaves on occasion. The land form 

 of Potamogeton natans is shown in Fig. 125, p. 196. P. varians, 

 a form allied to P. heterophyllus, Schreb., can exist for season 

 after season without being under water at all, tiding over the 

 winter by means of its bead-like tubers 5 . Even P. perfoliatus 

 has also been recently stated to produce a land form 6 , though 

 it is generally regarded as a typically submerged type, which 

 is incapable of terrestrial life 7 . 



Myriophyllum, Callitriche* and the Batrachian Ranunculi 

 (Fig. 126, p. 196) agree in producing land forms which are 

 close-growing and tufted. When Myriophyllum spicatum 1 , for 



1 Schenck, H. (1885). 2 Merj & (J882 1 ). 



3 Bachmann, H. (i 896), and Mer, . (i 882 1 ). See also p. 32, Ch. m. 



4 See Chapter n and Gliick, H. (1905). 



5 Fryer, A. (1887). Uspenskij, E. E. (1913). 

 7 Fryer, A., Bennett, A., and Evans, A. H. (1898-1915). 

 8 Lebel, E. (1863). 



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