The Morphology of Ruppia Maritima. 155 



has assumed the function of the primary root of the embryo. Such 

 an adventitious root, we have seen, ma}' occur in a similar way at 

 any node in the mature plant, just below the point of leaf-insertion. 

 Just what the group of cells at the base of the hypocotyl 

 does represent is difficult to say definitel}'. Murbeck thinks that 

 they may represent calyptrogen and calyptra (1902, p. 18). This 

 is, of course, possible, but it would be difficult to prove. We may 

 be sure of this much, however, that from their position, appearance, 

 and development, they bear some relation to the now functionless 

 primary root. 



Another interpretation of this whole thickened hypocotyl with 

 its curious basal cells seems plausible, namely, that practically the 

 whole swollen area itself represents the primar}^ root or radicle 

 which has been by degrees metamorphosed into a storage - organ. 

 That this is actually what has happened would be difficult to prove, 

 for it is dangerous to laj^ much stress on the form and position of 

 the storage organs. The strongest grounds for such an opinion are 

 drawn from a comparative morphological study. The embryo of 

 Zannichellia, e. g., is very similar to that of Ruppia. Although 

 Wille considers (1883, p. 7) that the small caplike body at the base 

 of the hypocotyl comprises the entire root, Campbell's figures and 

 description (1897, pp. 50, 51 and PI. V, figures 120, 122, 123) go 

 to show that practically the whole hypocotyl is a root structure 

 and the small body at its base is the root cap. 



In Zannichellia the primary root functions for a time during ger- 

 mination (Wille, 1883, p. 8). The absence of a distinct plerome 

 and periblem in what has been called the hypocotyl of Ruppia may 

 be accounted for by the degeneration of this tissue, its assumption 

 of the function of storage, and the transfer of its functioning power 

 as a root to the adventitious root. 



Trans. Conn. Acad., Vol. XIV. 11 December, 1908. 



