Fig. 366.
Stigmaria attached to a trunk of Sigillaria.[315-A]
In a specimen of one of these, represented in the annexed figure ([fig. 366.]), the spread of the roots was 16 feet, and some of them sent out rootlets, in all directions, into the surrounding clay.
The manner of attachment of the fibres to the stem resembles that of a ball and socket joint, the base of each rootlet being concave, and fitting on to a tubercle (see [figs. 367] and [368.]). Rows of these tubercles are arranged spirally round each root, which have always a medullary cavity and woody texture, much resembling that of Sigillaria, the structure of the vessels being, like it, scalariform.
Fig. 367.
Surface of another individual of same species, showing form of tubercles. (Foss. Flo. 34.)