The Morphology of Ruppia Maritima. 



103 



in the embrj'o, does not persist; the sole representatives of 



the root system are small slender adventitious roots arising at the 



nodes (PL VII, fig. 36, r). These occur singh' 



or rarety in pairs and are unbranched. Each 



root, in the earl}' stages of its development, is 



surrounded b}' a sort of pocket formed from 



the secondar}^ groAvth 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, rli). 



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 



roots are successively put forth from new nodes, of Dortion' of root- 



the older roots becoming graduall}' discolored stock and root ; col^ 



and ultimately dead, together with the stem coleorrkiza; ;-;i,root 

 , , ' 1 • • nairs ; rs^ rootstock. 



or rootstock whence they originate. >< about 1-^. 



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 alread}' given seems necessar}-. 



Irmisch (1858, pp. 44-45) has described at some length the re- 

 lation of root to leaf arrangement in Ruppia rosiellata, 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 

 mantima. 



The root is developed at the node, at one side of the leafbase, 

 and in the comparativeh' rare cases where a second root is de- 

 veloped at the same node (PI. Ill, 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 : — 



