152 
DR JOHN M ‘LEAN THOMPSON ON 
extremely xerophytic life conditions. The transitional types of dermal appendages, 
however, supply a peculiarly distinctive character, and, while they may be expressive 
of special adaptation in a physiological xerophyte, they serve, at the same time, to 
justify the recognition of Stromatopteris as generally distinct from Gleichenia. 
With Platyzoma it has no close kinship, and indeed they have little in common 
beyond the hallmarks of a xerophytic existence ; for Platyzoma shows sporangial 
advance with a relatively primitive, though somewhat anomalous, vegetative con- 
dition, but Stromatopteris is conservative of the structural and sporangial characters 
which are considered typical of the G-leicheniaceous stock. It is, then, believed that 
Stromatopteris is worthy of recognition as a distinct monotypic genus, closely allied 
to Gleichenia, but clearly distinguished from it by well-marked peculiarities of form 
and construction. 
Summary. 
The chief facts obtained from the herbarium specimens available of Stromatopteris 
have now been described. At some points the account has been less complete than 
would have been the case if undamaged plants had been available. The absence of 
perfect specimens has rendered impossible a definite conclusion regarding the form 
and position of the main axis in the growing plant, and it has likewise been im- 
possible to determine whether or not the mature sporophyte of Stromatopteris is 
rootless. Development has been necessarily omitted. But the fuller facts relating to 
mature form and structure which have been acquired may help towards establishing 
the position which this plant should hold in relation to other ferns. 
The habit of the plant is chiefly notable in relation to the vertical position of the 
branched portions of the axis, and the apparently terminal position which is, at times, 
assumed by the leaves as an accompaniment of displacement and abortion of the leaf- 
bearing branches. The plant is, in fact, of a xerophytically reduced type. The 
lower portions of the axis show dichotomous branching, but suppressions may occur 
leading towards complete abortion of a branch. The leaves are developed distally 
on the branch-system, and are produced singly on a branch or in small numbers. 
The development of the leaf is accompanied by the arrest and displacement of the 
supporting axis, and the dominating leaf may thus appear to be a direct upward con- 
tinuation of the axis. The arrest of the axis which accompanies leaf-formation may 
be complete or incomplete, and when complete leads to the formation of a nodular 
swelling at the base of the dominating leaf. It is in the distal portions of the 
branch-system that abortion is most evident, but it may also appear in the lower 
branch-system. It may similarly appear in the leaves themselves, and lead to the 
formation of leaves of a reduced type. Branchings of the leaf may occur. It is 
probable that such branchings are of the same nature as those seen in the forma 
furcata of many ferns. The erect position of the branched portion of the axis, and 
the dominance of the leaves over the supporting -branches, are features in strong 
