The Morphology of Ruppia Maritima. 103 
in the embryo, does not persist; the sole representatives of 
the root system are small slender adventitious roots arising at the 
nodes (PI. VII, fig. 36, 7). These occur singly \Y 
or rarely in pairs and are unbranched. Each see 
root, in the early stages of its development, is 
surrounded. by a sort of pocket formed from aie 
the secondary growth of the epidermis of the 
stem. After the root has broken through the 
tip of this pocket, the latter remains as a 
persistent sheath or collar at its base. A zone 
of root hairs appears on every root, developed 
from specialized piliferous cells (Textfig. 21, rh). 
As to the length of the root, I have measured 
specimens 20 cm. long, but a much shorter 
length is the general rule. 
The life of the root is comparatively short; \ 
for as the stem advances in its growth, new $ 
: Figure 21.—Sketch 
roots are successively put forth from new nodes, — 6¢ portion of root- 
the older roots becoming gradually discolored — stock and root; co/J, 
and ultimately dead, together with the stem Coleorrhiza ; 7, root 
eae hairs ; 7s, rootstock. 
or rootstock whence they originate. >< about 14. 

B. Root Arrangement 
Since the laws of the root arrangement in Ruppia are often obscure, 
as regards both the roots themselves and also their orientation with 
respect to the leaves, a somewhat more detailed description than 
that already given seems necessary. 
Irmisch (1858, pp. 44-45) has described at some length the re- 
lation of root to leaf arrangement in Auppia rostellata, and for a 
more detailed account I would refer to him. The following is to 
some extent a confirmation of his observations as referred to Ruppia 
maritima. 
The root is developed at the node, at one side of the leafbase, . 
and in the comparatively rare cases where a second root is de- 
veloped at the same node (PI. II, fig. 10), it assumes a correspon- 
ding position at the other side of the leaf base. 
Since the roots, when occurring singly, invariably issue from the 
same side of the stem, and since their orientation with respect to 
the leaf of the node is as just stated, the following facts or laws 
of arrangement are established :— 
