OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
65 
In even the smallest known branches of the former plants we find exactly the same type 
of organization as we do in the largest and most matured stems. We invariably have a 
central cellular medulla, which becomes fistular at a very early period, and which is 
surrounded by a ring of distinctly separated vascular bundles or wedges, each one of 
which has a well-marked longitudinal canal at its inner angle. The same conditions 
recur with the greatest exactness in the cone which I have described in the Transactions 
of the Literary and Philosophical Society of Manchester as being that of a Calamite; 
but in Calamostachys all these conditions are reversed. Here we have neither a cellular 
medulla nor a fistular cavity. In their place we invariably have a solid, central axis of 
barred vessels, such as we find only in the very young twigs of Lepidodendroid plants 
and in Aster ojohyllites. The only indication of the structure of the exogenous zone of 
the parent stem of Calamostachys which we have found is that represented in Plate YI. 
fig. 38. Here, at all events, we might have expected to discover some trace of Cala- # 
mitean arrangements, had these been Calamitean strobili; but nothing of the kind 
appears. It is as unlike the exogenous zone of a Calamite as it is like the corresponding 
tissue found in the roots of Asterophyllites. The central axis does not display the very 
definitely triangular form seen in that of Asterophyllites, but there is a decided approach 
towards it ; and we detect a further indication of a trifid arrangement in Plate VI. 
fig. 38, at the two points indicated by the letters d d. Each of these constitutes a 
centre, on either side of which the radiating laminae of the exogenous zone converge 
towards the letter d as they proceed outwards. I presume that a similar point may have 
existed to the left of the lower part of the figure indicated by d' ; but here, as already 
mentioned, the tissues have been accidentally displaced by some disturbing force 
masking their primary condition. 
We shall find a similar tendency to that just described recurring in the roots of 
Aster oyhyllites. 
It appears to me that the number and symmetrical grouping of the nodal appendages 
round the central axis of Calamostachys is not without significance. In its normal and 
almost invariable condition each verticil, whether of leaves or of sporangia, exhibits 
some multiple of 3. Thus we have six sporangiophores and twelve foliar divisions of 
the barren verticils. Whatever these facts indicate they are in harmony with the 
prevalence of the trimerous type of structure so characteristic of the stem of Astero- 
phy Hites. 
After balancing these various facts and arguments, I am led to the conclusion that 
Calamostachys Binneyana has much closer affinities with Asterophyllites than with 
Catamites. With the latter it has no one structural feature in common. There is no 
solitary point in which the two plants resemble each other. The resemblance of the 
fertile sporangia of Calamostachys to those of JEquisetum has been combined with the 
foregone conclusion that the Catamites were Equisetaceous plants, in leading to the 
belief that the two were parts of the same plant ; but I cannot conceive of any 
conditions in which the stem of a Catamites could be prolonged into that of the Cala- 
MDCCCLXXIV. K 
