Boodle.— Anatomy of the Gleicheniaceae . 709 
attempt to obtain similar preparations, after the material had 
been left in spirit for about two days, entirely failed. This 
indicates the possibility that in the other species of Gleichenia 
and in the Hymenophyllaceae and Schizaeaceae, where the 
azoblue-test failed, the callus-reaction might be obtained by 
means of some preliminary treatment, e. g. boiling for a short 
time ; though this is unnecessary in the case of Pteris and 
many other Ferns. That is, either callus may be present, 
but masked by being infiltrated with some other substance, 
which prevents the appearance of the characteristic stain, or 
there may here be a body slightly differing from callus, but 
easily converted into it. Poirault (’ 93 , p. 191), also working 
with dried material, mentions having found callus in the 
sieve- tubes of the Gleicheniaceae. Unstained preparations 
from dried material in two or three species showed bodies 
strongly resembling callus-rods and knobs. 
A layer of parenchyma separates the metaphloem from the 
xylem (see Fig. 3). The xylem forms the central part of the 
stele. Its diameter varies roughly with that of the rhizome. 
In G. polypodioides it measures only about ^ mm., while in 
G. pubescens it reaches i-J mm. In several species the xylem 
has an approximately circular outline in the internode 
(Fig. 1, x), but becomes oval near the node (Fig. 2). 
G . flabellata and G. pubescens are two of the species, which 
have a circular xylem. In others it is distinctly lobed, and 
the lobes have a definite relation to the protoxylem-groups, 
e. g. in G. dichotoma (Fig. 14, x), G. dicarpa , G. circinata . 
When the xylem is lobed the metaphloem forms a thicker 
layer, and is composed of larger sieve-tubes in the bays of the 
xylem than opposite the lobes. The structure of the xylem 
can be seen by comparing Figs. 2, 3, 4 and 5. The general 
low-power view of the xylem in Fig. 2 ( G. flabellata) shows 
that the tracheides are arranged in chains and groups, 
separated by parenchyma as in Lygodium . The essential 
point of difference lies in the position and nature of the 
protoxylem. In Gleichenia there are several small groups 
of annular and spiral protoxylem-tracheides placed a short 
3 A 2 _ 
