xxxii Proceedings. [February 20th, igi2. 



Professor W. H. Lang, M.B., D.Sc, F.R.S., read a paper 

 entitled, " Branching in the Ophioglossaceae." 



The branching in Ophioglossaceae is of special interest for 

 comparison with that known for the Zygopterideae and Hymeno- 

 phyllacae. Branches occur occasionally in all three genera of 

 the Ophioglossaceae. So far as is known those of Ophiog- 

 lossum always spring from lateral roots. In Helminfhostachys, 

 what appear to be dormant or vestigial axillary buds, were 

 discovered by Gwynne Vaughan, and are constantly found. 

 Similar dormant buds were found by Bruchmann in young 

 plants of Botrycliium littiaria, and explain the axillary branching 

 described by Roeper and Holle. 



Examination of young and old plants of Botrycliium Iiitmria 

 has shown that a dormant bud is constantly present in each leaf- 

 axil. In some cases a vestigial vascular supply, in the form of 

 two slender and evanescent strands of tracheides, springs from 

 the margins of the subtending leaf trace. Two examples in 

 which, owing to destruction of the apex of the main axis, a 

 lateral branch had developed, were studied in detail, and the 

 vascular supply to the branch traced from the adaxial side of the 

 leaf-trace. In one case the stele of the branch became con- 

 tinuous at a higher level and for a short distance with the stele 

 of the main axis. 



Two fragments of the rhizome of Helminihostachys, each 

 bearing a developed axillary branch, were studied in detail. 

 This examination completely confirmed the interpretation of the 

 structures found by Gwynne Vaughan as vestigial buds. The 

 supply to the branch came from a development of accessory 

 xylem outside the ordinary xylem of the stele of the rhizome, 

 and not from the leaf-trace. This vascular supply is traceable 

 from about the level of the departure of the subtending leaf- 

 trace to the anterior end of the leaf-gap, where the vestigial bud 

 is normally situated. From here onwards it has assumed the 

 structure of a small stele like that found in young plants, and 

 shortly afterwards the brancli exhibits its own proper cortex. 



