The Morphology of Ruppia Maritima. 155 
has assumed the function of the primary root of the embryo. Such 
an adventitious root, we have seen, may 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 definitely. 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 primary 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 lay 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 thypocotyl 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. Acap., Vol. XIV. iB Decemper, 1908. 
