337 
section Hemidictyum, along with the two species of Aspleni- 
dictyum and Hemidictyum marginatum, all three very dis- 
_ tinct in habit. Although I now place Ceterach after Hemi- 
dictyum it is not that I consider it has any relationship, 
| ‘but merely on account of having no ally for it, I place it 
_ à$ an anomalous genus at the end of the tribe. 
Sp. C. Officinarum, Willd. (v v.) (Grammitis, Sw. ; Scolo- 
pendrium, Sm.). 
. . O8s.—Found in rocky places, and on old walls in this 
b. country, and throughout Europe and the temperate regions 
of the Northern hemisphere generally, In Madeira the 
fronds attain a large size, and which by some authors has 
been described as a distinct species under the name of 
|. C. aureum, ; 
` CHARACTERS OF TRIBES AND GENERA. 
L4 
B. Ring of Sporangia horizontal, central. ` 
Beet, 1.—Sori discal, punctiform, naked, rarely indusiate. 
Tribe 24.—GLEICHENE. (Plate 24). 
(Gleicheniacee, R. Br.) 
. Ons.— This Tribe includes a peculiar group of Ferns, 
S consisting of about thirty described species, technically 
distinguished from Polypodiacee by the sporangia being 
Surrounded with a horizontal ring generally at right 
angles with the axis of attachment. This direction of the ` ` 
ring is common to the whole of true Gleicheniacee, but in = 
Matonia it is partially oblique. | : 
. Independent of the structure of the sporangia, Gleiche- — 
niacewe are readily known from all other Ferns by their ` ` 
fronds being once or many times dichotomously branched ` — 
or flabelliform (two species excepted, which have simple ` 
fronds), ` 
