728 Boodle. — Anatomy of the Gleicheniaceae. 
In the species examined the stomata were restricted to the 
lower surface of the pinnules. One interesting arrangement 
in the xerophytic form, G. dicarpa , var. alpina , is worth 
mentioning. Each pinnule was, in a sense, revolute. As 
seen in transverse section the right and left half of the lamina 
formed two semicircles springing from the midrib, and the 
lower surface of the midrib bore flat scales, which were spread 
out horizontally and reached the margins of the lamina. 
Consequently the lower surface of the latter, which bore the 
stomata, formed the lining of a chamber, to which the scales 
acted like a lid. The mesophyll in this variety was more 
lacunar than in species, which appeared less or scarcely xero- 
phytic. The upper epidermis was also thicker- walled. 
Gleichenia pectinata. 
This species differs from all those described above in * 
possessing solenostelic structure. Figs. 24-27 illustrate the 
internodal and nodal structure of G. pectinata. Only dried 
material was obtainable, which accounts for the collapsed 
condition of most of the soft tissues. Fig. 24 is a photograph 
of a transverse section of the stele in the internode. The 
position of the protoxylems, inner and outer phloem, & c., 
is shown in the diagram of the same section (Fig. 25). The 
phloem on both sides of the xylem is mostly crushed, but 
here and there patches of it were in fairly good condition, and 
when examined under the high-power showed elements, which 
in the characters of their refractive walls, sieve-plates, &c., were 
typical Fern-sieve-tubes. It was in the internal phloem of 
this species that callus-knobs were recognized by using the 
azo-blue test. The central space in Fig. 24 was due to 
the inner endodermis having become torn, and the central 
sclerenchyma having dropped out. The xylem contains very 
large scalariform tracheides, and these are separated from 
one another by chains and groups of parenchymatous cells. 
The xylem is mesarch with, at this point, 8-9 groups of spiral 
protoxylem-elements. The structure is essentially the same 
as in other species of Gleichenia possessing a lobed xylem, 
