16(3 
On the History, Histological Structure, 
the larger tubes often pass through them from one side to the other 
(Plate XXXI., Fig. b, and Plate XXXII., Fig. a) ; and finally no 
medullary cellular tissue has ever been detected in them either by 
Dr. Dawson or myself, although the delicate-walled smaller tubes 
are well preserved, and may often be seen passing through them. 
If we now turn to the longitudinal section, we shall find much 
additional light thrown on the structure of this fossil. Under a low 
power (Plate XXXII., Fig. a), we see that the large tubes are not 
parallel, but that while their general direction is the same, they 
pass in and out in an irregular manner. They are, moreover, con- 
tinuous tubes without any discoverable termination. This is well 
shown in the singularly faithful drawings by Mr. Blair. I have 
most carefully again and again searched for the termination of a 
tube without success, except in one instance, when examining a slide 
with my friend Dr. Wittroek, the Algologist, I detected a horizontal 
septum, with the slightest indentation on the periphery of the 
wall, showing that it was not accidental to the fossilization, but 
that it had been present in the original structure. Although I 
marked the slide I have been unable again to detect the particular 
tube, else I would have had it figured. Here again I am in direct 
opposition to the statements and drawings of Dr. Dawson. He 
says, “ The wood cells are seen to be much elongated, and to 
terminate in conical points.” * And his figure! clearly shows this, as 
well as that (fig. 24) on plate ii. of his ‘ Pre- carboniferous Plants,’ 
though the text is somewhat modified, but not really corrected. 
Dr. Dawson has obviously been misled by the way in which one 
tube is hid by the passage over it of another. I had pointed out 
this defective observation on his part in my letter, as is evident 
from the note already quoted. How far this letter led to the 
modification of the text I cannot tell, but it is remarkable that 
the text differs from the plates in so important a point. 
With a higher power than that employed in Fig. a, the true 
nature of the tubes becomes more apparent. The wide spaces 
which separate them are as obvious here as in the transverse section, 
and the character and direction of the smaller tubes are clearly 
exhibited (Plate XXXII., Fig. c). If one may speak of one blunder as 
more gross than another in Dr. Dawson’s description of this fossil, 
that designation must be given to the error which he has made in 
connection with these small tubes. In every description published 
by him he says, “ Cells of pleurenchyma with a double series of 
spiral fibres.” This error in observation (persevered in after I had 
pointed it out to him in his own specimen) suggested the Taxineous 
affinity of the fossil, and influenced the drawings of the plant. I 
have already shown that the large tubes cannot be called pleuren- 
chymatous cells, and now I have to show that the “ double series of 
spiral fibres ” are not inside the large tubes, but are independent 
* ‘Quart. Joum. Geol. Soc.,’ vol. xv., p. 485. f L. c., p. 484, figure 5 b. 
