708 Boodle . — Anatomy of the Gleicheniaceae. 
usually of about the same tangential diameter as the endo- 
dermal cells, but are more nearly isodiametric. In the 
mature stem they do not generally show definite radial 
seriation, but in a transverse section of the young rhizome 
of G. dicarpa the pericyclic cells at many points were neatly 
arranged in radial rows, which did not come to an end with 
the pericycle but were continued through the endodermis 
to the next two or three layers of the cortex. At other 
points the radial rows were disturbed by displacement of 
cell-walls, but this was so slight that their radial origin 
was still fairly clear. The pericycle therefore appears to be 
cortical in origin. 
The protophloem forms a practically unbroken layer of 
small elements (sieve-tubes and phloem-parenchyma) similar 
to those in Lygodiutn , and taking a strong stain when treated 
with Klein enberg’s haematoxylene. The layer of proto- 
phloem may be recognized in the low-power photograph 
(Fig. i, pph .), and is shown as it appears under the high- 
power in Fig. 3 (pph.). The metaphloem forms a continuous 
zone within the protophloem, and consists of large sieve-tubes 
and a certain amount of parenchyma. The walls of these 
sieve-tubes are seen to be of considerable thickness when the 
section is mounted in glycerine-jelly or in weak glycerine 
(s.t., Fig. 3). Numerous refractive granules are often seen 
adhering to the walls as in other Ferns. As the sieve-tubes 
were not found to differ in any important point from those of 
Lygodium , as to the character of their sieve-plates, &c., there 
is no need to enter into detail, except as to the presence or 
absence of callus. Sections of the rhizome and petiole of two 
or three species of Gleichenia were tested with azoblue, but 
gave no evidence of the presence of callus. Subsequently the 
rhizome of G. pectinata was examined. In this case dried 
material was used, and a section was cut, and tested with 
azoblue, soon after the material had been softened by boiling 
in water. It was then found that a few of the sieve-tubes 
showed distinct callus-knobs on their sieve-plates, similar to 
those which occur in Pteris aquilina (Boodle, ’ 01 , p. 399). An 
