The Morphology of Ruppia Maritima. 113 



merged Potamogetons, such as P. filiformis, have a similar root 

 structure. 



Another plant, whose roots resemble closel}' in internal structure 

 those of Kuppia, is Althenia filiformis. Epidermis, exodermis and 

 cortex are practically identical with the same tissues in Ruppia, and 

 although Prillieux's (1864) description and figures of the bundle leave 

 much to be desired, there is evidentl}" a strong resemblance to 

 Ruppia. 



The structure of the mature root of Cymodocea apparentl}' differs 

 entirely from our plant, most certainly in the composition of the 

 central cylinder, according to Bornet's (1864) description and figure. 



D. Functions of the Root 



As is well known, the two main functions of the root are — 1. to 

 absorb water and watery solutions from the soil, and 2. to act 

 as organs of attachment. That these functions are both of much 

 importance in the roots of land plants is an established fact ; that 

 their relative importance assumes the same proportions in submerged 

 plants is not so well established. 



Some authorities, such as Sachs (1887) and Vines (1898), have 

 expressed the view that the roots of submerged plants are used 

 mainly as organs of attachment. Schenck (1886, pp. 57, 58) 

 modifies this somewhat, concluding that the absorption is of not 

 much importance, but may possibly supply mineral solutions from 

 the soil. 



Strasburger's (1891) view, as expressed in his work " Uber den 

 Bau und die Verrichtungen der Leitungsbahnen in den Pflanzen," 

 is similar to Schenck's. In the Bonn Textbook (1908, p. 165), 

 however, Noll says, " Wasserpfianzen .... vermogen Wasser und 



geloste Stoffe iiberall an ihrer Oberflache aufzunehmen Die 



in den Boden eindringenden Wurzeln vieler submersen Pflanzen 

 tragen aber zur Emahrung und zum Gedeihen dieser Wasser- 

 pfianzen wesentlich bei " — thus laying considerable emphasis on the 

 absorptive power of the root. 



Pond (1905) has indeed recenth' proved quite conclusively that 

 this absorption is of more importance than was formerly supposed — 

 to such a degree that, for example, in Ranunculus aquatilis tricho- 

 phyllus, one of the various submerged plants he has experimented 

 upon, specimens rooted in soil exceeded in growth those rooted in 

 clean washed sand 62.960/0. Similar results were obtained by him 

 with other submerged plants. 



