part 2] ANNIVERSARY ADDRESS OE THE PRESIDENT. XClii 



which the botanist is concerned is the origin of the two phyla of 

 plants, which may he styled the Irycopod phylum and the Fern 

 phylum. The Lycopods are essentially microphyllous, while the 

 Ferns are megaphyllous. The Upper Devonian floras contain 

 many plants with large fern-like fronds, and among the older 

 Devonian plants we find examples of branched axes which suggest 

 comparison with the plan of construction of a large fern-leaf, 

 except in the absence of leaflets. The question is, were the Ferns 

 and Lycopods both the offspring of a common ancestor, or do they 

 represent separate lines of evolution ? Dr. Halle suggests that 

 the views of 0. Lignier may be considered to derive some support 

 from certain old Devonian types. It may be, as Lignier believed, 

 that the small Lycopod leaf arose as a mere emergence such as we 

 see foreshadowed in Psilophyton, and retained in the living 

 Psilotum ; while the compound Fern-frond traces its evolution to 

 a modified branch-system on which numerous flat leaflets were 

 subsequently developed. The combination in Psilophyton gold- 

 schmidti of the spinous appendages on the main stem and the 

 bifurcate spineless branches may be regarded as symptomatic of a 

 common origin of the microphyllous and megaphyllous form of 

 foliage. In many living Ferns we see, as Halle points out, a 

 similar combination of the small scale-like leaf without chlorophyll 

 clothing the rhizome, the homologue of the green leaf of Lyco- 

 poclhim, and the large green frond derived from a system of 

 branches of some early precursor, such as the bifurcate lateral 

 branches of Psilophyton goldsclimidti. On the other hand, there 

 is a danger of over-estimating the importance of resemblances be- 

 tween the form of branching in one plant and that in another. 

 The line of evolution of Lycopodiaceous plants is, I think, clearly 

 indicated ; and we have no adequate reason for assuming any 

 meeting-place between the Fern and the Lycopod phyla. Among 

 the earlier terrestrial plants parallelism of development may 

 safely be postulated : the fronds of Ferns were probably derived 

 direct from the thallus of some algal ancestor, unconnected with 

 that which produced the small-leaved Lycopods. 



An extinct plant combining in the sum of its characters mor- 

 phological features which no longer occur together in the same 

 family or group is usually considered to be, if not a ' missing link ', 

 at least a signpost on the evolutionary road pointing the way to 

 some ancestral stock whence were derived descendants which 



