Bower.— Studies in the Phytogeny of the Filicales . 459 
Lindsaya. Odontosoria. 
The close relation of the individual sori of the marginal series in Sacco- 
loma only involves their indusium, of which the ‘ upper ’ flap is merged into 
an apparent leaf-margin, though the ‘ lower 5 flaps of the individual sori 
remain separate. But in Lindsaya and some other Davallieae both flaps 
merge, while the receptacles also become continuous as a marginal, or 
apparently intramarginal, flange. The clear indication of what has occurred 
is found by comparison of individual cases where the fusion is incomplete. 
Some of these will be described below. 
On the other hand, the vascular construction of the stem of Lindsaya , 
as described by Tansley (‘Ann. of Bot.,’ xvi, March, 190a), is of a type which 
may be held as more primitive than that of any solenostelic Fern. We see 
the stage of structure, which in Lindsaya is permanent, rapidly passed 
through in the runner of Cibotium Barometz , and it probably figures in the 
early development of many Ferns. In fact, the axis of Lindsaya appears 
to have retained permanently a condition which is only rudimentary and 
transitional elsewhere. Thus, anatomically, Lindsaya stands on a relatively 
low plane, though its soral condition is relatively advanced. 
The developmental tendencies of the Davallieae, as they affect the sori, 
are towards their passage from the margin to the lower surface, and towards 
their fusion. These modifications, combined with some others, do not 
necessarily progress on parallel lines, with the result that there is some 
difficulty in the grouping of the different forms, and synonymy is profuse 
and confusing. The two plants on which observations have been made are 
Odontosoria retusa , (Cav.) J. Sm., and Lindsaya lancea , (L.) Bedd. The 
former was supplied from the Edinburgh Botanic Garden, the latter collected 
in Jamaica. The material of the latter was insufficient for a complete study 
of the development, but it sufficed to show that the condition is essentially 
similar to that seen in Odontosoria , which was more fully examined. As in 
Saccoloma , the first indication of the future sorus is a flattening of the 
margin on the young pinnule (Fig. 17, a). The construction of it has been 
by successive segments cut off from a marginal cell, which still retains its 
identity, but it lags behind the last segments in its activity of growth, so 
that these overtop it right and left (Fig. 17, b). That on the abaxial side 
takes the lead slightly over the other, so that the receptacle, in which the 
marginal cell is still visible, takes an oblique slope. This is maintained 
even in later stages, though, owing to stronger growth, the adaxial or 
‘upper ’ lip of the indusium soon overtops the abaxial or ‘lower’ (Fig. 18). 
The vascular tissues develop in the region below the receptacle, and as 
a vascular commissure there links the several veins together laterally, each 
vertical section shows a more or less prominent mass of tracheides spreading 
below the receptacular surface. On the latter the sporangia begin to 
