and Affinities of Nematoffihycus Logani. 
167 
Fig. 2. 
structures external to them ! They are indeed the small circular 
openings seen occupying the spaces between the large tubes in the 
transverse section, and which in the longitudinal section we find to 
be slender tubes passing in and out among the large tubes in a 
more or less oblique direction. An intelligent or educated observer 
would at a glance see the true nature of these smaller structures, 
though the great number of them is not at once apparent. This is 
owing to the delicate nature of their walls, as well as to the fact, 
which I have already stated, that the fossilizing mineral which re- 
places their tissues is of the same colour and structure as that which 
fills the spaces in which they occur. Continued observations with 
good light and a good objective (the drawings were made with a |th 
of Ross) will exhibit their great number and their irregular direction, 
so well expressed by Mr. Blair in Plate XXXII., Figs, b and c. 
That the strong terms in which I am compelled to speak of 
Principal Dawson’s descriptions and drawings may be justified by 
those who have not access to his memoir, I have copied in fac- 
simile a drawing from plate ii. of his ‘ Pre-car- 
boniferous Plants,’ in which, as in other drawings, 
the print is made to tell the erroneous observation 
which Dr. Dawson has given to it. This figure 
is thus explained : — “ Prototaxites Logani, three 
(two) wood cells, showing spiral fibres and obscure 
pores at a a, 300 diameters.” It is not a restora- 
tion. There is a note at the foot of page 18 of 
‘ Pre-carboniferous Plants ’ which is in strange con- 
trast to the text. How far it owes its existence 
to my letter I cannot say, for in it I pressed on 
Dr. Dawson’s notice how completely the existence 
of these smaller tubes destroyed his whole theory. 
The note is as follows: — “In some of the more 
perfect specimens the fibres appear as if connected 
with each other by fine reticulations, or by the 
dark bars of the thickened walls passing from 
one to another. This curious appearance it is ~ f ni „ . , 
to? ij j i • ti L \ Copied from Plate II., 
difficult to explain, it may either depend on the fig. 26 , of Dawson’s ‘Pre- 
state ot preservation ot the specimens, or on some 
peculiarity of structure at present unknown to me.” If Dr. Dawson 
knew anything whatever about a vegetable cell, and the formation of 
the spiral fibre in its interior, he would not have written such non- 
sense as the first sentence in this footnote. A little further reading 
or investigation would have saved him from the equally fatal blunder 
of describing coniferous disks or bordered pores on the walls of 
tubes which are not in contact, but are widely separated from each 
other. Principal Dawson will find that coniferous disks could not 
exist in such circumstances. The markings on which the notion is 
based are not common ; but in the slides I have examined I have 
