988 CHARACTERS OF TRIBES AND GENERA. 
distinct from Allantodia, especially as the general character 
of the fronds of Allantodia agrees with Hemidictyum. I 
nevertheless deem it best to retain it as distinct. 
Sp. H. marginatum, Presl (v ei, 
194.—Crreracu, Willd., in part (1810). 
Asplenium, sect. Hemidictyum, Hook. Sp. Fil. 
Vernation fasciculate, acaulose, becoming cæspitose. 
Fronds 2 to 12 inches long, sinuose-pinnatifid, the under 
side densely squamose. Veins forked; venules anastomo- 
sing, obscure. Sporangia unilateral, anterior. ndusium 
rudimentary. Sort oblong, the sporangia poiki 
through dense scales. 
Type. Asplenium Ceterach, Linn. 
Illust. Hook. and Bauer Gen. Fil., t.113 A. ; Moore Ind. | 
. Fil, p. 39 A. ; J. Sm. Ferns, Brit. and For., fig. 117. — 
Oss.—This genus is founded on a solitary species, which ` ` 
in habit, and the nature of its fructification, is so peculiar — ` 
that it has given rise to much diversity of opinion as to its — 
proper place in any arrangement, whether natural or arti- — . 
ficial. In my “Genera of Ferns” (1841) I stated that its — 
unilateral sporangia indicated it to belong to Asplenew, and `` 
that the imperfect or obsolete indusium was owing to the — 
suppression of that organ, caused by the density of the — 
 Squame on the under side of the frond. More recent - 
Observations have shown the presence of a narrow linear 
i indusium, which is more evident in the large fronded 
species called C. aurea, of Madeira, than in the common 
. form. It must, however, be confessed that its peculiarities 
| prevent its association with any species of the asplenoid 
— tribe, except with Asplenium alternans of Wallich, already 
noticed. In the “Species Filicum" it is placed in the 
