1042 Chambers.—The Vestigial Axillary Strands of 
meristele. Text-fig. 4 shows that the meristele, a , passes slowly through the 
cortex until, just before it curves into the petiole, it divides to form the 
axillary branch, x, and the leaf-trace, /, which passes out into the petiole with 
# towards the adaxial and l towards the abaxial surface. The other meri¬ 
stele, b , figured in the diagram, reaches the petiole and there divides into 
branch strand, x\ and leaf-trace, Each axillary branch strand gradually 
curves away from the leaf-trace and ends in a small protuberance of tissue 
on the adaxial surface. 
Conclusion 
An examination of fossil and recent forms has led Scott 1 to mention 
a suggestion that dichotomy may have been the primitive type of branching, 
and that axillary branching may have arisen at first as a reduced dichotomy, 
the subtending leaf being really borne on one arm of the dichotomy. Tansley 2 
applies the dichotomy theory also to axis and leaf. He brings forward in 
support of this theory the fact that there is a certain similarity in structure 
between the stele of the axis and the leaf-trace in the Botryopterideae and 
the Hymenophyllaceae. In T. javanicum the meristele is radial in structure, 
but differs from the axis in having central protoxylem. The meristele 
divides into two unequal parts to form branch and leaf-trace, which are not 
alike in structure, since the branch strand exactly resembles the axis and the 
leaf-trace shows signs of dorsiventrality and has two distinct groups of 
protoxylem. This does not really militate against Tansley’s theory, since 
Trichomanes is a recent form, and has undergone a certain amount of 
specialization. In the ancient forms included in the Botryopterideae it is 
often very difficult to distinguish between axis and leaf-trace. Dr. M. Benson 
has pointed out this difficulty and the great similarity between axis and 
petiole in her paper on Botryopteris antiqua , Kid. 
The conical mass of parenchyma in which the axillary strand of 
T. javanicum ends recalls the parenchymatous mass, described by Gwynne- 
Vaughan 3 in Helminthostachys zeylanica as projecting from the stele of the 
axis to meet the base of each axillary canal. This tends to confirm his 
suggestion that these bodies c represent the last indications of vestigial 
axillary buds \ 4 Bower 5 has recently pointed out in his paper on Ophioglos - 
sum palm alum that the trend of modern work is to relate the Ophioglossales 
to the Botryopterideae on account of the similarity in sporangial dehiscence, 
stipular structure, and heterophylly. To this list may now be added the 
1 Studies in Fossil Botany, p. 318. 
2 The Evolution of the Filicinean Vascular System. New Phyt. Reprint, 1908, Lecture 1. 
3 loc. cit. 
4 Renault, in his publications in 1878, regarded the Botryopterideae as related directly to the 
Hymenophyllaceae and Ophioglossaceae. See Studies in Fossil Botany, p. 640. 
5 Annals of Botany, April, 1911. 
