CHAP. XLIV REED-SWAMP OR REED-FORMATION 189 



(b) In addition to long linear leaves rising from a rhizome or radiating 

 from the base of the flowering axis, there are tall culms bearing inflo- 

 rescences, as may be seen in Typha, Acorus, Butomus, and others. 



(c) Tall haulms with long distichous, spreading leaves, as in Phragmites 

 and other grasses. 



The character common to all is that the dominant, mainly monocotylous, 

 plants which give the stamp to the vegetation, are tall, slender, upright, 

 and unbranched. Even in Ranunculus Lingua and in Rumex Hydrola- 

 pathum there is a recurrence of the same habit which thus suggests 

 an adaptation of obscure significance. It may, however, be pointed out 

 that these tall slender shoots easily bend to breeze or current, and elasti- 

 cally recover ; this is specially true of the unbranched stems of plants 

 such as Scirpus palustris, or the tall, long leaves projecting above the water 

 from the stems of Typha and Sparganium. 



Nearly all the species are perennial herbs, or, like Ranunculus scelera- 

 tus, biennials. Special hibernating and propagative organs are produced 

 by Sagittaria, in the form of stem-tubers on runners. An occasional 

 woody plant, such as Salix cinerea or Alnus glutinosa, may also occur. 



Among the plants of reed-swamps many are almost devoid of 

 protection against desiccation they are mesophytes ; but others are 

 xeromorphic, for one finds among them leaves with a profile-lie in Iris, 

 rolled leaves in Cladium, juncoid shoots in Juncus and Scirpus, dense 

 hairiness in Epilobium hirsutum, and so forth. Aerenchyma is very 

 widely represented in plants of the reed-swamp. 



Geographical Distribution. Associations of this same stamp are 

 ubiquitous on the Earth. Phragmites, the reed, is extraordinarily wide- 

 spread ; over an area of many square miles it forms impenetrable associa- 

 tions (phragmiteta) in the Danube delta, in deltas of the Caspian Sea, 

 and Lake Aral, and even in Australia ; on the Syr-daria it attains a 

 height of 6 metres and endures salt water quite well, while in Lusatia 

 in Germany its variety pseudo-donax attains nearly 10 metres. 1 It can 

 grow in water 3 metres in depth. In Mediterranean countries this reed 

 forms communities, and is sometimes accompanied by Arundo Don ax 

 and Erianthus Ravennae, two grasses which are often even 5 and 6 metres 

 in height. As an illustration of its capacity of adjusting itself to external 

 conditions, we may mention that on the shores of the North Sea and of 

 many inland lakes it produces long epigeous runners. 2 



Extensive reed-swamps of Glyceria spectabilis on the saline soil of 

 Neusiedler Lake assume the form of veritable ' grass-forests ' 2 metres 

 in height ; the same is true of Cyperus syriacus in Sicily, and in an 

 exaggerated degree of C. Papyrus on the Upper Nile, where this, together 

 with Panicum pyramidale, Phragmites communis, Typha australis, and 

 others, give rise to a ' sudd-formation ' 3 ; the shores of Valencia Lake in 

 Venezuela are fringed with dense reed-swamps of Typha domingensis, 

 which exceeds man's height, and the same is true of the cyperaceous 

 Malacochaete Tatora on the shores of Lake Titicaca. 



In Virginia, according to Kearney, 4 there occur similar reed-swamps, 



1 According to Ascherson und Grabner 1898-9. 



2 Illustrations in Warming. 1906 ; Schroter und Kirchner, 1902. 



3 Broun, 1905. * Kearney, 1901. 



