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THE PHRAGMITES-TYPHA ASSOCIATION 



In shallower water than the Cares association is the Phragmites- 

 Typha association. Ecological conditions seem to be much the same 

 as for the Car ex except that the water is shallower. The plants of 

 this association are rooted in muddy soil a few decimeters below the 

 water-level and have their vegetative parts comparatively high in the 

 air, where they are exposed to the di'ying effects of the wind and sun. 

 The cattail (Typha) is, in a small measure, adapted to these condi- 

 tions by having its broad lea.ves edgewise with the noonday sun. 

 Adaptation would seem hardly necessary since the plants can obtain 

 water as fast as it is evaporated. Even on the hottest and driest days, 

 Typha never appears wilted, but PJiragiuites may be quite noticeably 

 wilted. Each of the dominant species dominates the situations in 

 which it is located. Very dense plant families are formed on ac- 

 count of the close method of vegetative reproduction. Although 

 these two species seldom intermingle, they conform exactly to the 

 limits of water-depth in which either will grow. For these reasons, 

 either may be farther out or nearer the shore, or a family of one may 

 be between two families of the other, and this without change of wa- 

 ter-depth. There is very little room for secondary species, and the 

 few that do occur are relics or invaders of other associations. When 

 this association appears in the ditches along the railway, the dominant 

 species is usually Typha on account of the much greater production of 

 its seeds. In two pools Typha angustifolia alternates with T. lati- 

 folia. Hybrids between these two species occasionally occur, and 

 there is a form having two completely separated spikes of pistillate 

 flowers in addition to the staminate spike. 



LIST OF THE SPECIES OF THE PIIRAGMITES-TYPHA ASSOCIATION 



Dominant Species 

 Typha latifolia Typha angustifolia 



Phragmites coiniiiunis 



Secondary Species 

 Acorns calamus (a very little) Oxypolis rigidior 

 Utriciilaria vulgaris anicricana Scirpus atrovirens 

 Scirpiis rnbrotinctns 



Relic Species 

 Care.v lanuginosa (a little) Proscrpinaca palnstris 



Invading Species 

 Scirpus valid us 



