FROM THE LOWER COAL-MEASURES. 51 
There is again a gap between IX. and X. corresponding to the main set of longitudinal 
sections. The interval was not less than 1:6 cm. 
In X. the smaller meristele z' has again divided into two strands, each about 2 mm. in 
diameter, lying side by side (Pl. 7. fig. 5). All these are now free from the stele. 
In this and the succeeding sections the large meristele « approaches very near the 
neighbouring meristele on the right; the intermediate tissue is somewhat obscured by 
injury, but I have not obtained any evidence of a fusion between these two meristeles. 
In the course of the next six sections little change takes place; in the uppermost of 
the series, however, No. XVII., there are distinct signs of a severance of the large 
meristele into two parts, along a line nearly parallel to the surface of the stele; the 
approaching severance is indicated by the presence of well-marked incisions on both 
sides (see Pl. 8. fig. 6). 
This is as far as the series carries us. The derivation of the meristele from the stele 
and its subdivision are well shown up to a certain point, but not so far as to explain the 
origin of the actual leaf-trace strands. 
The meristele 8 will now be traced to compare with the former case. This meristele 
lies on the opposite side of the stele to that just described. 
At the bottom of the series, in Sections I. and II., we find a large flat mass of tissue 
protruding from the stele, to which it is attached near its middle, like the head of a 
hammer. The total length of the protrusion, in the direction tangential to the stele, is 
no less than 20 mm., while its breadth varies from 2 to 3 mm, It may have been more 
prominent in the natural condition than it now appears. There are two or three free 
strands adjacent to the outgrowth, which not improbably sprang from it at a lower level. 
In the first section figured (III.) the left-hand end of the protrusion has just 
separated, as a distinct strand 3x 1:5 mm. in diameter (Pl. 7. fig. 1, 98). This minor 
meristele may be compared to that given off from « at an early stage (see above, p. 50), 
but its fate appears to be different; in the present ease it moves off rather rapidly to 
the left, but cannot be identified with certainty beyond Section IX. (Pl. 7. fig. 4); 
probably it breaks up into leaf-trace bundles, but they cannot be definitely distinguished 
from neighbouring strands. 
Returning to the main meristele 9, we find that Section V. shows important changes 
(Pl. 7. fig. 2). The whole protrusion has here separated from the stele, except perhaps 
for a slight connection remaining to the left of the centre. At the same time the mass 
is just splitting into two unequal parts, the left-hand meristele (9) being 45 X8 mm., 
and the right-hand (8) 11x 3:5 mm. in diameter. At Section VII. the separation of the 
two meristeles from the stele and from each other is certainly complete, so that 6 
becomes free at a lower level than « In VIII. the separation is very obvious (see 
fig. 3). | 
dud, IX. (beyond a gap) considerable changes have taken place. The smaller 
meristele, 9', has here moved to a distance of a millimetre or more from the main pers, 
B; the interesting point, however, is that the latter - fusing, on the p iem another 
meristele, whieh up to this point has been quite independent. On — fig. 3 
(from Section VIII.) with fig. 4 (from Section IX.) this fusion will be evident. In 
