384 EQUISETALES 
(Bornia) Renault describes} for B. radiata, Brongn., how the fructifications 
are Simple, or interrupted in their length by verticils of leaves, which 
render the -spike itself, so to speak, articulated and of very variable 
length. The condition of these spikes is then different in proportion, 
rather than in essential points from that described for Phyllotheca (Fig. 
197), and so curiously reproduced in the abnormal Equiseta described 
above (Fig. 196). This again differs from Calamostachys mainly in the 
number of the sporangiophores which intervene between the successive 
leaf-whorls. The tracts which bear the sporangia being thus variable, it 
would appear that the Lguzsetum-type is merely an extreme case, in 
which the whole series of sporangiophores which form the terminal 
strobilus are collectively above the last leaf-sheath, and that last leaf sheath 
is of a reduced type, and appears as the annulus. 
It is obvious that in the present state of our knowledge the case is 
not proved either for the phyllome-theory of the sporangiophore in the 
Equisetales, which is out of harmony with the known facts in the fossils, 
or for the non-phyllome theory, which is certainly a less obvious explanation 
of the simple strobilus of Zguzsetum. But the balance of evidence is 
strongly in favour of the latter, as without undue pressure it covers the 
whole area of facts, including those relating to the fossil Equisetales.? 
1 Bassin Houiller d’ Autun et d’Epinac, p. 81. 
2Tt is necessary briefly to mention another view, advanced by Jeffrey (A/em. Boston 
Soc. of Nat. Hist., vol. v., pp. 184-5), as applicable to those Calamitean cones where 
the bracts in each whorl are stated to be double the number of the sporangiophores. 
He suggests that the pairs of the sterile leaves were really dichotomously divided dorsal 
segments of sporophylls, of which the sporangiophores were the ventral segments. It is 
necessary to remember, however, that in the best known cones of Calamostachys the 
bracts of successive whorls alternate, while the successive whorls of the sporangiophores, 
considered by themselves, are strictly superposed (Scott, Progressus, p. 158): this fact 
appears to be fatal to Jeffrey’s suggestion, as will be obvious if the arrangement be 
plotted out diagrammatically in one plane. It will then appear that the proposed scheme 
would only apply to each alternate whorl of bracts, not to them all. There is also 
against it the fact that in the Equisetales at large the arrangement of the cone with the 
bracts approximately doubling the number of the sporangiophores is only one among 
several different arrangements: the proposed scheme is quite inapplicable for Archaco- 
calamites or for Eguisetum, and equally so for Palaeostachya (cf. Hickling, /.c.). 
Akin to Jeffrey’s theory, though not coincident with it, is that of Lignier (Awdl. de la 
Soc. Linn. de Normandie, Caen, 1903, p. 162, etc.), which also is based primarily on the 
data fur the cone of Calamostachys, and upon comparisons with the Sphenophylls. His 
view is that the sporangiophores in Calamostachys are the result of concrescence in pairs 
of fertile lateral lobes of the leaves forming the verticil. The anatomical facts are 
derived from Renault (Bassin Aouiller et Perm. a’ Autun et a’ Epinac, iv., 2, p. 130, and 
Pl. Ix.); the details shown in his figure, 6, of the single transverse section partially 
depicted would accord with the theory; but the evidence seems insufficient, and there are 
the following positive objections to it. First, ‘there is no structural evidence in the 
sporangiophores themselves of Calamostachys, or in any other of the Equisetales, of the 
presumed fusion. Secondly, in the single drawing of a complete transverse section of 
the cone of C. Zez/leri by Renault (dc, Pl. ix., Fig. 5) there are 14 sporangiophores, but 
only 27 sterile bracts: so that the numerical relation does not hold in the one case on 
