SECTION V 



CLASS II. HELOPHYTES. MARSH-PLANTS 



CHAPTER XLIII. ADAPTATIONS. FORMATIONS 



x'Vmong aquatic plants are included all plants whose assimilatory 

 organs are submerged, or, at most, swim on the surface of water ^ ; marsh- 

 plants or helophytes include all those which normally have their roots 

 under water or in soaking soil, but, like land-plants, raise their foliage 

 branches above the water-surface. It has already been pointed out ^ 

 that there is no sharp hmit between marsh-plants and land-plants. 

 Moreover, many marsh-plants are more or less ' amphibious ' and plastic, 

 so that they can change their structure according as they are submerged 

 or not.^ 



Marsh-plants and bog-plants are confined to shallow, still, or gently 

 flowing water, and to soil that contains a large amount of water (appa- 

 rently more than eighty per cent.) at least for a prolonged period. The 

 soil is loose, often very loose and soft, also usually rich in humus in the 

 form of peat or mud."* 



ADAPTATIONS 



1. Marsh-plants, Hke aquatic plants, are largely perennials.^ But in 

 marshes that are completely dried up during the dry season annual species 

 may prevail. 



2. Many marsh-plants readily produce adventitious roots and possess 

 horizontal rhizomes or runners ; in Europe such is the case with Equise- 

 tum limosum, Iris Pseudacorus, Phragmites, Typha, Acorus, Butomus, 

 Scirpus lacustris and S. (Heleocharis) palustris, Eriophorum angustifohum 

 and E. alpinum, Sparganium, Carex acutiformis, C. rostrata, and other 

 >pecies, Cladium Mariscus, and other Monocotyledones, Lysimachia 

 \ulgaris and L. thyrsiflora, Ranunculus Lingua, Sium latifolium (with 

 roots that produce buds) and S. angustifohum. 



Caespitose plants with a small power of vegetative migration or 

 devoid of such a power are exemplified by Ly thrum Salicaria, Cicuta 

 virosa, Alisma Plantago, and Rumex Hydrolapathum. Plants of this 

 form often grow partially on their own dead fragments by which they are 

 jirradually lifted upwards ; one obvious reason for this is that water is 

 raised by capillarity in the sponge-like tufts formed by the interwoven 

 remnants of stems, leaves, and roots ; such is the case with Eriophorum 

 vaginatum, Carex stricta, C. paniculata, and many other species. 



In addition there occur plants showing other modes of growth ; for 



' See Chap. XXVII. ' See p. 131. 



^ Costantin, 1897; Schenck, 1884, 1886; Massart, 1902. 



' See p. 61. ' See p. 100. 



