ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 733 
of pales, The pales, or at least their bases, have remained, while most of the 
delicate young tissue of the organ which they protected has perished, leaving a hollow 
in the axis of the whole structure. The specimen is: so remarkable, that we 
considered it worth figuring and describing, though its nature must at present remain 
problematical. 
C.—Tue Roor. 
1. Connection between Root and Stem. 
We have already briefly recorded our discovery that Kalowylon Hookeri was the 
root of Lyginodendron Oldhamium.* We will now bring forward the evidence on 
which this conclusion is based. 
It has long been known that the stem of Lyginodedron bore appendages quite dis- 
tinct from the petioles. Several examples of these are described and figured in 
Memoir IV., p. 387, figs. 11, 12, 14, 16, 22, and 24. The appendages in question are 
shown passing out more or less horizontally from the wood, and traversing the cortex. 
They were at that time regarded as branches, though another specimen—which was 
really, no doubt, of the same nature—was already recognized as being probably a root 
(loc. cit., fig. 7). 
A number of better preserved specimens also showing these organs in connection 
with the stem have since been obtained. These afford evidence— 
1. That the appendages in question were of endogenous origin, and presented in all 
respects the characteristic structure of roots. 
2. That these roots are identical with the fossil previously described as Kaloxylon 
Hookeri. 
We will first state the facts which prove that the appendages are morphologically 
roots. 
Adventitious roots, with the rarest exceptions, are of endogenous origin ; they arise 
from deep-seated tissues (pericycle or endodermis), and have to grow out through the 
cortex of the parent stem. Hence they are readily distinguished from stem-branches, 
which are almost always of exogenous origin, arising from superficial tissues. <A 
section of the cortex of the parent stem, passing through the base of an adventitious 
root, will show the latter as a complete organ, possessing a cortex and epidermis of 
its. own; a corresponding section at the base of a branch would show only the 
vascular tissues, which connect the bundles of the branch with those of the stem. 
We have the clearest evidence that the appendages of the Lyginodendron stem were 
of the former kind. Plate 19, photograph 8, represents part of a transverse section of a 
large stem. An appendage, which evidently made a sharp bend close to its base, is 
* ‘Proc. Roy. Soc.,’ vol. 56, 1894. [Mr. T. Hice arrived independently, and almost simultaneously, 
at the same conclusion, but solely on the evidence of comparative anatomy. See ‘Mem. and Proc. 
Manchester Lit. and Phil. Soc.,’ ser. 4, vol. 9, Session 1894-5. (D. H.S., Dec. 14, 1895.)] 
