A GIGANTIC FLOATING PLANT. 
477 
®hort, the longest yet found attached to the stem, 
four feet and a half in length. The extent of 
these branches, when outstretched and perfect, 
probably from twenty to thirty feet.* The 
Surface of each branch is covered with spirally 
•disposed tubercles, resembling the papillae at the 
^ase of the spines of Echini. From each tu- 
bercle there proceeded a cylindrical and probably 
Succulent leaf ; these extended to the length of 
Several feet from all sides of the branches. (PI. 
'^6, Figs. 10. 11.) The leaves, usually in a com- 
pressed state, are found penetrating in all direc- 
hons into the sand-stone or shale which forms 
the surrounding matrix ; they have been traced 
to the length of three feet, and have been said to 
be much longer. f 
* It appears from sections of a branch of Stigmaria, engraved 
y bindley and Hutton, (Foss. Flora, PI. Ifi6), that its interior 
a hollow cylinder composed exclusively of spiral vessels, 
'^''d containing a thick pith, and that the transverse section 
^’^hibits a structure something like that of Conifer®, but without 
'Concentric circles, and with open spaces instead of the miiriform 
bssue of medullary rays. No such structure is known among 
‘■'''ng plants. 
fhese cylindrical branches are usually depressed on one side, 
P''obablythe inferiorside (PI. 56, Figs. 8. ab. and 10. b.)\ adjacent 
^0 this depression there is found a loose internal eccentric axis, or 
"'oody core, (PI. 56. Fig. 10. a.) surrounded with vascular fasciculi 
^^at communicated with the external tubercles, and resembled 
*^*‘0 internal axis within the stems of certain species of Cactus. 
1" All these are conditions, which a Plant habitually floating 
"'flh the leaves distended in every direction, would not cease to 
‘''''intain, when drifted to the bottom of an Estuary, and there 
gradually surrounded by sediments of mud and silt. 
