244 Lady Isabel Browne. 
annulus made its first appearance as a group of apical cells. This 
view was largely based on the apparently Schizaeaceous affinities of 
the Upper Carboniferous Senftenbergia where the annulus appears 
to be an apical cap of cells, not a ring enclosing one or more cells. 
But recent discoveries have thrown doubt on the filicinean character 
of many of these fern-like fructifications, and it is therefore not 
impossible that Senftenbergia (which, however, resembles the 
Schizaeaceae, in that its sporangia are non-soral) is the male 
organ of a Pteridosperm. But even if the annulus is homologous 
in the two orders there remains the important difference that 
the Gleicheniaceae are soral and the Schizaeaceae non-soral. 
In view of the striking similarities of the vegetative organs of 
both orders we are driven to one of two alternatives: either 
that in the Schizaeaceae the sporangia represent reduced monangic 
sori, or that fresh sporangia have been developed in the evolution 
of the Gleicheniaceous sorus, either by septation of a single 
sporangium or by interpolation of fresh sporangia. Since the 
monangic condition is exceptional in the Ferns it is probable 
that the single sporangia of the Schizaeaceae represent reduced 
sori. But it should not be forgotten that Professor Bower 
has shown that there is every probability that in the evolution of 
Gleichenia dichotoma an interpolation of supernumerary sporangia 
has occurred. Thus the similarities between the two orders are 
sufficient to indicate that the common stock from which they are 
derived lies considerably less far back than do the common an¬ 
cestors of Gleicheniaceae and Botryopterideae or of Gleicheniaceae 
and the filmy Ferns. 
Matonine^;. 
Matonia, the only genus of the Matonineae, shows a considerable 
range of anatomical complexity. Its stem may possess two con¬ 
centric solenosteles of which the inner encloses only a pith (37), or 
the inner solenostele may contain in the centre of the pith a strand 
of xylem, while in other cases this central strand is itself con¬ 
verted into a third solenostele (39). The evolution of polycyclic 
solenostely has recently been so fully traced in this journal that it 
would be superfluous to do more than briefly to recapitulate the 
explanation given. It has been shown conclusively that the internal 
solenosteles arise in the ontogeny as a local thickening of the edge 
of the gap left by the departing leaf-trace in the stele immediately 
outside it; the strand thus formed, as it increases in size, 
