45 
The So-called Phloem of Lepidodendron. 
of the meristem-band, both in this stem and in Lepidodendron 
fuliginosum does not abut directly on the thicker walled tracheal 
elements, but it is separated from the wood by a few layers of cells. 
Beyond the unlignified tracheids, occupying the innermost portion 
of Scott’s phloem, there are several layers of very delicate and 
rather flattened cells which make up the rest of the ‘ phloem ’ zone ; 
these cells appear in longitudinal section (fig. 2, 6) as very short 
elements with a depth somewhat less than their tangential diameter 
as represented in Scott’s figure. This tissue in fact is a homogeneous 
band of short thin-walled cells, in which the formation of new cell- 
walls was in active progress when the plant was killed ; the structure 
is essentially distinct from that of typical phloem and there are no 
elements which can be compared with sieve-tubes. Scott’s “phloem 
zone ” corresponds in position with the band of tissue in which 
Weiss recognises the cambium in Lepidodendron fuliginosum, while 
the phloem of the latter author is represented in the Dalmeny plant 
by a zone which lies beyond the limits of Scott’s figure. Both 
observers agree in considering that I am in error in my view that 
we have not as yet discovered any typical phloem in Lepidodendron , 
but they apply the term phloem to two distinct tissues, the ‘phloem’ 
shown in Scott’s figure is my meristematic zone, while that so 
named by Weiss is my secretory zone. The great breadth of the 
meristematic zone, as shown in the Dalmeny stem (figs. 1 and 2, C), 
is one of the peculiar anatomical features of the genus; the narrow 
cambium of recent plants was represented by a broad band which 
may be compared with the meristematic region of Draccena and a 
few othe genera. Beyond the meristem band in the Dalmeny stem 
we find a tissue (figs. 1 and 2, S), distinguished by the irregular and 
disorganised character of the elements and by the occurrence of 
tangentially elongated or oval spaces, which is not included in the 
area figured by Scott. This band, shown at 5 in figs. 1 and 2, is 
certainly identical with that which I have called the secretory zone 
in Lepidodendron fuliginosum \ and which Weiss designates phloem. 
The identity of this tissue (secretory zone) in the two species may 
be readily recognised by a comparison of PI. II., figs. 9 and 15 Sc., 
PI. III. fig. 16 Sc in the published description of the Scotch stem 2 
with text-figures 2, 3 and 5 and PI. III., figs 3 and 4 and PI. IV., 
fig. 12 in my paper on Lepidodendron fuliginosum 3 . 
1 Seward, 1899. Figs. 2, 3 and 5,S, PI. III., figs. 3 and 4, S; PI. 
IV., fig. 12. 
2 Seward and Hill, 1900. 
s Seward, 1899. 
