76 STUDIES IN FOSSIL BOTANY 



they are identical in structure with our Calamostachys, 

 and some of them are known to have been hetero- 

 sporous. 



Secondly, according to Grand'Eury, we have the 

 great division of Arthropitys, or Calamites proper, of 

 which Asterophyllites represents the foliage, or rather 

 the leaf-bearing branches. There appears to be good 

 evidence for the connection between them. The wood, 

 where preserved, is of the simple type of Calamites or 

 Arthropitys, described in detail in the last chapter. The 

 characteristic arrangement of the spikes is in panicles 

 borne on branches with the foliage of Asterophyllites 

 (cf. Fig. 25). The terminal leaf- bearing branches 

 were distichously arranged, with crowded whorls of 

 narrow acicular leaves, which here also were united 

 when young into a sheath (see Fig. 34). Associated 

 with the Calamitean stem, and in connection with the 

 Asterophyllitic foliage, is found Palaeostachya gracilis, 

 which was one of the forms of fructification belonging to 

 this type, a fact which agrees with Williamson's results, 

 but cones of the Calamostachys form also belonged to 

 this group. In fact, the whole position is rather para- 

 doxical, for to the stem known specifically as Calamites 

 cannaeformis (according to the characters of the medul- 

 lary cast) Grand'Eury attributes fructifications of two 

 different genera ! This shows that the so-called species 

 among fossils must not be understood in the same 

 sense as species of living plants. Grand'Eury himself 

 points out that these so-called species are rather of 

 generic value. It is no doubt impossible to recognise 

 strictly specific differences from the medullary casts, 

 and it is quite likely that stems with casts indis- 



