HICK : SOME RECENT ADVANCES IN BRITISH PALEOBOTANY. 47 
most cases the organisation is radial rather than dorsiventral, and 
we can usually recognise — 
1. A central cylinder or stele, in which is a delicate, eccentric, 
vascular strand, 
2. A zone surrounding this, corresponding to the cortex of the 
stem, and made up of 
(a) An inner single layer of ** melasmatic " elements, and 
(b) An outer thicker layer of assimilating tissue. 
3. A single layered epidermis. 
The presence of a " melasmatic " layer in these leaves, corres- 
ponding in its histological characters and position with that of the 
stem, is an indication that they belong to the same type of Calamites 
as the stems referred to. 
The Fruits. — In referring to the fruits of Calamites \n 1891, I 
summarised very briefly the conflicting views held by palaeobotanists 
with respect to the sporangiferous spike known as Calamostachys 
Binneyana Schimp., views which had already been set forth at full 
length by Mr. Cash.'' Reference was made to the fact that in the 
tirst part of the General, Morphological, and Histological Indexf to 
his Memoirs, Williamson modified the views he had previously 
expressed at various times so far as to include the spike in the great 
group of Calamai'iew, but it was pointed out that this was not the 
same thing as aflirming that it was the fruit of Calamites. Moreover, 
in so placing it he did not associate it with the genus Calamites, but 
with the fossils which he then named Asterophyllites, but which he 
subsequently referred to the genus Sphenophyllum.X '^^^ discrepant 
views as to the affinities of this spike were attributed to the absence 
of any published specimen which showed, in a demonstrative manner, 
the structure of the axis, and the suspicion was expressed that that 
axis would yet prove to have a Calamitean structure, and that in 
some cases at least this "fruit" would turn out to be that of 
Arthropitys. 
This suspicion was almost immediately converted into a certainty. 
* Proc. of the Yorksh. Geol. and Polyt. Soc. , 1887, pp. 414 et seq. 
t Mem. and Proc. of the Manch. Lit. and Phil. Soc, ser. 4, vol. iv., 1890-91. 
X Williamson and Scott, Phil. Trans., vol. clxxxv., B. (1894). 
