ii 4 STUDIES IN FOSSIL BOTANY 



Sphenophyllum might represent the foliage of some of 

 the Calamites. This mistake arose from the fact that 

 the finely-divided or linear form of foliage, often occur- 

 ring in species of Sphenophyllum, sometimes bears a 

 great external resemblance to the foliage of the 

 branches known as Asterophyllites, which really be- 

 longed to Calamitean stems. This resemblance may 

 easily lead to confusion, in cases where we have to deal 

 with imperfect specimens without structure, but of 

 course it proves nothing as to any connection between 

 the two groups of plants. External characters of the 

 foliage are as unsafe a guide among fossil as among 

 recent plants. If the genus Galium had existed in 

 Carboniferous times, we should no doubt have often 

 been puzzled to distinguish its remains from those of 

 Sphenophyllum or of Calamites. It is the specimens 

 with their structure preserved which give the only safe 

 clue to the interpretation of the rest. The discussion 

 of the affinities of Sphenophyllum will best be post- 

 poned until the next family has been considered. 



II. Cheirostrobeae 



4. Cheirostrobus. — This very distinct type of strobilus 

 was originally described from a single specimen of the 

 actual cone, and another fragment containing the 

 peduncle. The specimens, of which two more have 

 since come to light, were derived from the famous 

 deposit at Pettycur, on the Firth of Forth, belonging 

 to the Calciferous Sandstone series, at the base of 

 the Carboniferous formation. The fossil is therefore 

 of great antiquity, and is, in fact, among the oldest 



