ANATOMY AND AFFINITY OF CERTAIN RARE AND PRIMITIVE FERNS. 373 
is known of it beyond its habit features. In the following pages it is shown that 
the characters of Llavea are of transitional type, and it is maintained that Lagasca’s 
foundation is fully justified by the facts of anatomy and reproduction. 
Habit. — -The stem is strong, erect, and beset with hairs and scales. The latter 
are discarded at maturity, leaving the axis straw-coloured. The leaves are long and 
typically tripinnate. The lower part of the leaf is sterile, and its pinnules are stalked 
and cordate. The upper pinnules are fertile and linear, with inrolled margins and 
a general pod-like appearance. At maturity the leaves are virtually naked, the 
pinnules are delicate but not of filmy texture, and their veins are prominent. 
According to Hooker ( Syn . Fil.), Llavea is a Mexican Fern growing up to a level 
of 7500 feet. The habit* is well shown in the leones Plantarum, 1841. 
The structural features here described have been investigated in a single specimen, 
for which I am indebted to Professor Bower. The plant came originally from 
Dr Goebel, Munich. 
Dermal Appendages. — The dermal appendages of the axis are lanceolate scales 
and unbranched hairs (figs. 28, 29). The scales are sessile, and are massed .around 
the leaf-bases ; the hairs are small, non-glandular, and hidden by the broad scale- 
bases. In our materials the only appendages found on the pinnules are a few hairs 
distributed along the veins. The scales are of an advanced type, and the simplicity 
of the hairs may be primitive. 
Axis. — The axis is almost erect, and bears the leaves in a loose spiral arrange- 
ment. The roots are mainly associated with the leaf-bases, and emerge from the 
cortex in branched groups. The ground-tissue is mainly storage parenchyma, only 
a narrow outer margin being sclerotic. The vascular cylinder is a simple solenostele, 
with short oblique gaps, towards the base of each of which an undivided strap-shaped 
leaf-trace is obliquely inserted. These points are shown in fig. 31, which represents 
a stelar reconstruction based on a series of transverse sections of the stem. They are 
further demonstrated in the series of diagrams comprised in text-fig. 8, and which 
represents consecutive transverse sections. 
Root .— 1 The root-traces are inserted on the stele mainly beneath the leaf-traces, 
and are frequently branched close to their points of origin (fig. 31). The root- 
structure shows no features of special interest. 
Leaf. — At the point of insertion of the leaf-trace on the stele the leaf-trace 
xylem has the form of a curved strap, thinner in its middle abaxial region than 
towards its margins. This is indicated in text-fig. 8 (/) and ( h ), l.t., in which the 
xylem is represented as black, the phloem as a dotted zone completely investing 
the xylem, and the endodermis as an unbroken line. Further out, the phloem on 
both sides of the thin zone of xylem is gradually replaced by parenchyma, and a 
break in the continuity of the tracheides follows. The condition established is 
represented diagrammatically in text-fig. 8 (a) — ( g ) and in fig. 26, which shows 
the details of construction of the abaxial portion of the trace. The interruption 
