744 Boodle. — Anatomy of the Gleicheniaceae. 
the petiole, and mentions the occurrence of phloem-fibres 
and of the central sclerenchyma in the petiolar bundle of 
G . dichotoma and G. rigida. He gives a diagram (PL VII, 
Fig. i a.) of a transverse section of the petiolar bundle of 
G. dichotoma , showing the form of the xylem-arch, and three 
diagrams (Fig. i, b ., c., and d.) illustrating the mode of consti- 
tution of the xylem-masses of the first two pinnae and the 
rachis. If one bears in mind that in these diagrams it is only 
the xylem that is shown, and that in his description (p. 1 55) 
‘ Biindel 5 represents ‘ xylem-mass/ the stages he gives may be 
taken as fairly accurate. 
Van Tieghem (’ 91 , p. 1376) describes the intermittent 
growth of the leaf in Gleichenia , due to the production of 
the dormant bud in the fork of the pinnae, and its subsequent 
growth as a rachis, and mentions the solid stele of the 
rhizome. 
Poirault’s work ( J 93 ) has been frequently referred to above, 
as he deals rather fully with the node and petiole of Gleichenia. 
In describing the rhizome of G. Boryi (p. 171) he speaks of 
the protoxylem-elements as narrow tracheides with very wide 
pits, so it seems that he must have missed the true protoxylem 
elements, which are spiral in that species, and probably in all 
except G. moniliformis. Poirault refers to the structure of 
Platyzoma , and, as mentioned above, gives an explanation 
of the manner in which its structure may have been derived 
from that of Gleichenia . 
