AJinities of the Genns I'othoQiies. 81 



The segments composing the fruit must, however, be 

 regarded as the homulogues of the internodes of the stem, 

 so, in all likelihood, the longitudinal ridges of the segments 

 of the fruit represent the furrows of the stem. 



In the spike we see that the longitudinal rows of spor- 

 angia do not alternate at the nodes, but pass continuously 

 throughout the whole fruit. 



In the genus Bornia, F. A. Eom. {Arcliceocalamites, 

 Stur), the furrows on the stem do not alternate at the nodes 

 as in ordinary Calamites ; and this well-marked character, 

 possessed by no other carboniferous fossil plant, so far as I 

 am aware, gives it an individuality which cannot be mis- 

 taken. Likewise in Pothocites we find that the longitudinal 

 elevations which bear sporangia do not alternate at the 

 nodes, but pass continuously throughout the whole length 

 of the spike ; and these ridges, I believe, are simply a 

 modification of the furrows of the stem. 



In the genus Calamites, where the furrows on the stem 

 alternate at the nodes, we have no reason to suppose that 

 this character would alter, even were they known to pro- 

 duce a PothociteS'like cone. But the fruit of the Calamites 

 is well known ; and whatever specific difi'erences there may 

 be in the described genera and species of their fructification, 

 they are always of the Volhmannia type ; hence it is not 

 at all probable that Pothocites belongs to this group of the 

 Calamitese. 



The dichotomous nature of the foliage is not, however, 

 restricted to the genus Bornia, 



Stur has described a small Sphenophylluni (^S. tenerrimum, 

 Ett. MS) * which also possesses dichotomously divided 

 leaves. But this is easily distinguished from Bornia 

 radiata, Brongn., by the leaves being much smaller and 

 less regularly dichotomous. The fruit of this plant has 

 also been described by Stur, and consists of a small Volk- 

 manyiia-Uke cone. 



Even on young branches of Bo7mia 7'adiata the foliage 

 is of considerable size. In the Pothocites from Eskdale 

 (PL IV. fig. 13) w^e have apparently only the remains of 

 the leaves, little more, indeed, than to show that leaves 



* Stur, Culm Flora, plate vii. p. 214. 



