432 Boodle and Hi ley. — On some Species of Gleichenia. 
vertical plane, and dichotomously in the horizontal plane. There is nothing 
resembling a nodal island in connexion with the branching. A ramular 
gap is generally present in both types of branching, but in one case of 
dichotomy the two steles were closed when they separated. 
It is considered that Eugleichenia represents a series of forms showing 
reduction from the typical Mertensia- type, represented, e. g. by G . flabellctta, 
and that Mertensia includes the most primitive species of Gleichenia , as well 
as the most advanced, viz. G. pectinata. The solenostelic structure of 
G. pectinata is to be regarded as derived from a protostelic Mertensia- type 
like that of G . flabellata. Among the possible modes of derivation of the 
solenostelic structure of G. pectinata from the type referred to, there is some 
probability that the course of evolution may have consisted in the formation 
of a pith and ramular gaps, followed by ‘ intrusion 9 of phloem, &c., through 
a ramular gap into the pith, and subsequent extension of the structure thus 
attained throughout the rhizome. 
List of Works referred to. 
Boodle (’01) : On the Anatomy of the Gleicheniaceae. Ann. Bot., xv, p. 703. 
Boodle (’ 03 ) : On Descriptions of Vascular Structures. New Phytologist, ii, p. 107. 
Bower (’ 08 ) : The Origin of a Land Flora. 
Faull (’01) : Anatomy of the Osmundaceae. Botan. Gazette, xxxii, p. 381. 
Goebel (’05) : Organography of Plants, Eng. ed. 
Gwynne-Vaughan (’03): Observations on the Anatomy of Solenostelic Ferns. Part II. Ann. 
Bot., xvii, p. 689. 
Gwynne-Vaughan (’08) : On the Real Nature of the Tracheae in the Ferns. Ann. Bot., xxii, p. 517. 
Jeffrey (’02): Structure and Development of the stem in Pteridophyta and Gymnosperms. Phil. 
Trans. Roy. Soc., B., cxcv, p. 119. 
Kidston and Gwynne-Vaughan (’07) : On the Fossil Osmundaceae. Parti. Trans. Roy. Soc., 
Edinburgh, xlv, p. 759. 
Poirault (’ 93 ) : Recherches sur les Cryptogames Vasculaires. Ann. Sci. Nat., Bot., 7 e ser., t. 18, 
p. 113. 
Tansley (’07) : Lectures on the Evolution of the Filicinean Vascular System. New Phytologist, 
vi, p. 135. 
EXPLANATION OF FIGURES IN PLATE XXIX. 
Illustrating Messrs. Boodle and Hiley’s Paper on the structure of Gleichenia. 
Lettering used in the illustrations : ab. ph . abaxial phloem ; c. cortex ; ep. epidermis ; ext. end. 
external endodermis ; ext. ph. external phloem ; int. end. internal endodermis ; int. ph. internal 
phloem ; m. medulla ; n.i. nodal island ; ph. phloem ; r.b. radial band ; r.t. root-trace ; sc. scleren- 
chyma ; xy. xylem. Protoxylem-groups are marked y 1,^2, See., y 3', y 3", See. 
All the figures are of Gleichenia pectinata. 
Fig. 1. Transverse section through internode, x 15. 
Fig. 2. Radial section through a node, x 7§. 
Figs. 3-7. A series of transverse sections through the nodal region of the rhizome, arranged 
opposite their correct positions in the longitudinal section (Fig. 2). x 15. 
Figs. 8 and 9. Transverse sections through a rhizome undergoing monopodial branching, 
x 11. 
