FILICES. 165 



towards the inside impinge so closely upon one another through the 

 pressure of the intermediate tissue that their contour lines seem to 

 be modelled one upon the other. Goppert's fine figure shows that 

 the scalariform tracheides of these woody bodies are arranged in regular 

 rows, which radiate from the interior sinus to the convex outer boundary. 

 At the same time the diameter is very different in the different masses 

 of wood ; some larger ones meet together in the centre, while other 

 smaller ones wedge themselves in between their shanks. The prepara- 

 tion which I was permitted to make from the original specimen also 

 showed what does not appear in Goppert's figures, namely that in the 

 sinus of each of these horseshoe-shaped cross sections and surrounded by 

 crushed tissue there lies a small vascular bundle of roundish outline, the 

 peripheral portion of which is everywhere of like structure and appears to 

 enclose within it the narrower elements, though these are not very clearly 

 seen (Fig. 15). Now where the structure is so anomalous, and especially in 

 the absence of more searching investigation into a form which is known 

 only in one or two fragments, it is very venturous to go at all beyond a 

 mere description of the facts. Still in studying the section the thought 

 forces itself on my mind, that in the horseshoe-shaped woody bodies we 

 may recognise secondary growths, the product of cambium, and that these 

 stand in some relation to the bundles in their sinus, either because the 

 bundle was collateral, or the zone of secondary tissue has been developed 

 on the periphery of the phloem. However this may be, we can do no 

 more at present than record the existence of this remarkable fossil ; let us 

 hope that we shall see our way in time to a fruitful comparison. 



Fern-stems in great numbers have been described from very various 

 formations. By far the larger part of them, being preserved in the form of 

 casts only, possess extremely small interest for the botanist. When remains 

 of this kind took the form of erect leafy stems with the leaves disposed in 

 spirals, they were included by Lindley and Hutton 1 and the earlier observers 

 under the collective name Caulopteris. This was certainly better than the 

 process of division commenced by Corda and pursued by various authors, 

 which being founded on unimportant characters could not possibly produce 

 rational genera, and which was less necessary because the number of the 

 stems in question was by no means unmanageable. The scars left by the 

 detached leaves are in many cases more or less plainly marked on the 

 periphery of the casts. The stems are not (infrequently clad in an armour 

 composed of spirally arranged leaf-stalks of different lengths, which crowded 

 together and interwoven with roots form a covering over the whole surface. 

 Casts of this kind, which do not even show the bundle-traces on the trans- 

 verse section of the leaf-stalk with any distinctness, are recorded in the 



1 Lindley and Hutton (1 . 



