496 
Gwynne-Vaughan. — On some Climbing 
Professor C. Eg. Bertrand 1 evolved an extremely neat and ingenious 
theory to bring the trace of Lygodiurn into line and explain it in terms of 
the adaxially curved trace. 
In order to test this theory and to find out whether the structural 
features warranted this idea, I investigated very thoroughly the traces 
of several species of Lygodiurn with confirmatory results, and I was led 
to examine the leaves of certain climbing species of Davallia , the near 
relations of which possess most typical C-shaped traces, to see whether 
similarity of habit had led them in the same direction of modification 
as appears to have been taken by Lygodiurn. 
The result appears to me to be a wellnigh complete confirmation 
in all essentials of Bertrand’s theory, with, however, a slight but interesting 
modification. 
[Bertrand and Cornaille in their explanation of the petiolar trace 
of Lygodiurn started from the c ternary chain ’ exhibited by the smaller 
traces of Osmund a. They based their account on the figures of Loxsoma 
Cunninghami as given by Gwynne-Vaughan, 2 and of Lygodiurn as given 
by Boodle, 3 their interpretation of the structure being indicated by the 
symbolic notation added to the figures which they reproduced. 
The change from the C-shaped trace to the type found in Lygodiurn is 
thus expressed : ‘ L'accentuation des plis inverses provoquee uniquement 
par un epaississement des masses du mctaxyleme, et bunion de ces plis 
inverses dans la surface de symetrie change completement le caractere 
de la trace, elle n est plus trace osmondeenne, mais bien trace onocleenne, son 
accentuation a produit les quadruples des Lygodiurn .’ 4 
It is clear from comparison of the annotated figures of the traces 
of L^ygodium and Loxsoma given in Bertrand and Cornaille’s plate that these 
investigators regarded the adaxial hooks of the xylem as still constituting 
part of the condensed 'xylem strand in Lygodiurn. The modification of 
Bertrand’s theory referred to above is that (as shown by Davallia fuma - 
rioides) the adaxial hooks exhibit all stages in disappearance before the 
Lygodiurn- like condition is attained. In connexion with this it may be 
noted that in Davallia acideata (Gwynne-Vaughan Coll., Slides Nos. 875-8), 
which has the same habit as D. fumarioides , the hooks appear to be 
absent throughout. 
The following facts relating to the vascular system of the petiole 
and its branches in four species of Lygodiurn are selected from notes which 
also deal with other features in the anatomy of this genus. They will serve 
as a restatement of the problem to which the structure of Davallia fuma- 
rioides affords the key.] 
1 C. Eg. Bertrand et F. Cornaille : Les caracteristiques des traces foliaires osmundeennes et 
cyathaceennes, exemples, modifications et reductions. Soc. Hist. Nat. d’Autun, 1902, 
2 Ann. of Bot., vol. xv, PI. iii, Fig. 7, A-E. 
? Ibid., PI. xix, Fig, 4. 
4 loc. cit., p. 9. 
