i i 2 Equisetales. 
may measure more than 12 cm. across and the sheaths on the 
aerial stem sometimes consist of as many as 120 teeth. In our 
living Equiseta no trace of secondary growth remains, unless the 
lateral wings of the bundles, or the nodal growth recorded by Mr. 
Cormack in Equisetum maximum, be a secondary growth (3). This 
is possible, but there is much doubt about the interpretation of both 
of these phenomena. This absence or reduction of secondary 
xylem, the reduction of its leaves, and its smaller size are the chief 
vegetative characters in which Equisetum differs from the Calamariae. 
As regards the cone of Equisetum it is certainly far closer to the 
more ancient Archaeocalamites than to Catamites. For reasons 
already given the present writer finds it impossible to derive the 
cone of Equisetum from that of any known Catamites, but it is quite 
easy to derive it from the apparently completely fertile cone of 
Archaeocalamites by way of Equisetites and, possibly, of Autophyllites. 
On the other hand the ancestors of Equisetum presumably early 
acquired the simple leaves and the alternation of the bundles at the 
nodes characteristic of Catamites, As Archaeocalamites was probably 
very near to the line of descent of Catamites, the latter genus and 
Equisetum may have had a common ancestor with a cone like than 
of Archaeocalamites and Equisetum, but with the bundles of the 
vegetative and reproductive axes already alternating at the nodes ; 
on the other hand this alternation may have been acquired 
independently in the ancestors of both genera. As regards 
Schizoneura, whose fructification is unknown, the superposition of 
the bundles at successive nodes warrants the supposition that it 
may have arisen from a type resembling Archaeocalamites. Phyllo- 
theca too, probably originated from an Archaeocalamitean type, 
possibly through a form like Pothocites by the sterilization and leafy 
development of occasional whorls of sporangiophores. 
LITERATURE QUOTED. 
1. F. O. Bower. “Studies in the Morphology of the Spore-Producing 
Members.” I.—Equisetineae and Lycopodineae.” 
Philosophical Transactions of the Royal Society of 
London. Series B., Vol 186, 1893. 
2. ,, “ The Origin of a Land Flora,” 1908. 
3. B. J. Cormack. “ On a Cambial Development in Equisetum." Annals 
of Botany, 1893. 
4. D. T. Gwynne-Vaughan. “ Remarks upon the nature of the stele of 
Equisetum." Report of the British Association, 
Glasgow, 1901, 
5. G. Hickling. “ The Anatomy of Palceostachya vern." Annals of 
Botany, 1907. 
