A GIGANTIC FLOATING PLANT. 477 
short, the longest yet found attached to the stem, 
was four feet and a half in length. The extent of 
these branches, when outstretched and perfect, 
was probably from twenty to thirty feet.* The 
surface of each branch is covered with spirally 
disposed tubercles, resembling the papillae at the 
base 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. 
56, Figs. 10. 11.) The leaves, usually in a com- 
pressed state, are found penetrating in all direc- 
tions 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. t 
* It appears from sections of a branch of Stigmaria, engraved 
by Lindley and Hutton, (Foss. Flora, PI. 166), that its interior 
was a hollow cylinder composed exclusively of spiral vessels, 
and containing a thick pith, and that the transverse section 
exhibits a structure something like that of Coniferee, but without 
concentric circles, and with open spaces instead of the muriform 
tissue of medullary rays. No such structure is known among 
living plants. 
These cylindrical branches are usually depressed on one side, 
probably the inferior side (PI. 56, Figs. 8. a 5. and 10. b.); adjacent 
to this depression there is found a loose internal eccentric axis, or 
woody core, (PI. 56. Fig. 10. a.) surrounded with vascular fasciculi 
that communicated with the external tubercles, and resembled 
the internal axis within the stems of certain species of Cactus. 
f All these are conditions, which a Plant habitually floating 
with the leaves distended in every direction, would not cease to 
maintain, when drifted to the bottom of an Estuary, and there 
gradually surrounded by sediments of mud and silt. 
