WATER AND SWAMP FLORA. 49 



by the rosettes of their floating leaves, as in sundew (Drosera inter- 

 media), water feather (Hottonia inflata), bladder wort (Utricvlaria 

 inflata), or by leaf -covered stems, as in hornwort (Ceratophyllum). 



LITHOPHYTIC AND LIMN^AN CLASSES. 



Of submersed hydroph} T tes rooting on the solid rocky bed of swiftly 

 running brooks two species of Podostemon occur in the mountainous 

 regions. They are moss-like plants, their roots provided with peculiar 

 organs by the aid of which they fasten themselves closely to the rocks. 

 More numerous species of different families constitute that association 

 of submersed hydrophytes which take root in the soft soil (Limnsean 

 associations). These are in some cases provided, in addition to the 

 immersed foliage, with peculiarly constructed shield-like leaves floating 

 on the surface, only their flowers being lifted above the water, of 

 which the following are examples: 



Castalia (water lily) . /Sagittaria natans (arrow leaf) . 



Nelumbo (water chinquapin) . Potamogeton spp. (pondweeds) . 



Nymphaea (spatter-dock) . Callitriche heterophylla (water star) . 

 Limnanthemum lacunosum (floating heart) . 



Others have the foliage entirely suomersed and of one form, as 

 water crowfoot (Batrachium divaricatum), bladderworts ( Utricularia 

 vulgaris and U. purpurea), water milfoils (Myriopkyllum spp.), with 

 their leaves finely divided; Yallisneria, with long strap-shaped leaves,- 

 and numerous pondweeds (Heteranthera, Najas spp., Philotria, Zanni- 

 chellia, and Ruppia), with the leaves from narrowly lanceolate to linear. 

 These Limnsean aquatics, with their stems mostly emerging from the 

 water at flowering, but their seeds ripening beneath it, form the fre- 

 quently very dense vegetation of ponds, lakes, and semistagnant 

 waters of the estuaries. Of this association, the species are especially 

 numerous in the Coast plain. 



PALUSTRIAX CLASSES. 



This association embraces the halophytes and fresh-water plants 

 which root in a water-soaked soil, with their leaves and flowering 

 stems above, and frequently their bases alone surrounded by water. 

 They are nearly all perennials, with stout roots or strong running root- 

 stocks (rhizomas), and cover the extensive open marshes of the tide- 

 water regions and river alluvium. Large monocotyledonous plants of 

 various kinds form the characteristic feature of this vegetation, of 

 which the following are representatives: 



Phragmites (tall reed) . Scirpus spp. (bulrush) . 



Spartina spp. (cord grass) . Cladium effusum (saw grass) . 



Zizania, Zizianopsis (water rice) . Scirpus maritimus (triangular-stemmed 



Typha spp. (cattail) . bulrush) . 



15894 4 



