Manchester Memoirs, Vol. xli. (1896), No. 1. 13 



of the stele of Lepidodendron, which in some respects 

 resembles that met with in our plant. But in these cases 

 it would seem that the detached smaller segment soon 

 becomes changed into a radially symmetrical stele, 

 similar, in essential points, to that from which it 

 originates, a condition of things which has not been 

 found in Rachiopteris cylindrica. According to Williamson, 

 this mode of branching in Lepidodendron is associated 

 with the formation of fruit-spikes or strobili, into the 

 axes of which the branches of the stele, successively 

 formed by unequal division, are distributed. While 

 there is a possibility, then, that in our plant the lateral 

 appendage may be some form of fruit or an organ axial 

 in its nature, the character of its stele is rather opposed 

 to such an interpretation than in favour of it. 



Fig. 6, which is taken from No. 102, shows what are 

 probably the relations in space between the axis and its 

 offshoots. At A and B we have two normal axes which 

 have apparently arisen by the dichotomy of a common 

 podium. Just below A is a section, a, of what appears 

 to be a root, while another, r, is seen just above B. 

 Below B, at s, is one of the unknown lateral appendages. 

 Symmetry of arrangement would suggest a lateral ap- 

 pendage above A, but the periphery of the latter is at 

 the extreme edge of the preparation, and it is impossible 

 to say whether such an appendage was or was not 

 originally present. The stele of B is undergoing un- 

 equal division in a plane at right angles to that which 

 contains all the other sections. 



What is Rachiopteris cylindrica ? 



Whatever interest or importance may attach to the 

 anatomical details set forth in the preceding pages, it must 

 be admitted that they help us but little towards a know- 

 ledge of the position which Rachiopteris cylindrica should 



