8 Stopes, a Neiv Fern from the Coal Measures. 



choose any such complicated fraction seems more than' 

 the conditions justify. In living plants it frequently 

 happens that there is a slight twisting of the line of 

 insertion which makes it difficult to determine the phyllo- 

 taxy from a small piece of the plant. In the case of a 

 fossil, therefore, in which has been detected a slight' 

 bending of the axis, and of which there is at best but a 

 few internodes from a single specimen, 1 prefer to choose 

 the simplest common fraction which comes out nearly 

 right, and therefore provisionally state the phyllotaxy to 

 be |. (See Text-fig. i.) 



Fig. I. — Plan of the petioles in a transverse section, shewing the 

 phyllotaxy to be |. {Slide T 13.) 



The branching of the meristele from the main axis 

 is very simple, a group of tracheides (apparently including 

 one or two of the supposed protoxylem elements) separates 

 from the outer part of the main mass, and bends away 

 from it (see Figs. 3 and 4). In transverse section this 

 group appears oval or bean-shaped, gradually taking the 

 form of a thick slightly bent arc as it leaves the stele. 

 The convex side of the meristele is from the first directed 

 towards the main axis. As it passes out the crescent form 

 becomes more accentuated, and the ends begin to bend 

 slightly round to form the C of the free petiole. In the 



