326 
Dr. Greville on two new species of Ferns 
In looking over a small collection of Cryptogamous plants re- 
cently gathered in the island of Tahiti by Dr. Sibbald and sent 
by him to Professor Balfour, I found two specimens (only two, 
alas !) of a moss which a single glance convinced me must belong 
to the genus Spiridens ; and the capsules being in a perfect state 
enabled me to determine this at once in the most satisfactoi-y 
manner. The resemblance which it bears in general character 
to S. Reinwardtii is so marked, that at first it seemed doubtful 
whether it might not be a mere variety, but a more careful 
inspection rendered the specific distinctions quite apparent. 
The new species is a smaller and more slejider plant, six to 
nine inches long or more, the leaves scarcely more than half 
the size, the capsules more cylindrical and the subulate termina- 
tion of the operculum considerably longer and finer. It is under 
the microscope, however, that the most characteristic features are 
perceived to exist in the leaves ; the margin of which in S. Rein- 
wardtii is distinguished by a broad flat border closely and sharply 
toothed ; in the new species by a very narrow thickened border 
remotely toothed. Without entering into a minute description, 
uncalled for in so brief a notice, the following specific characters 
may be assigned to the two mosses ; — 
-S'. Reinwardtii (Nees) ; foliis late raarginatis, acute dentatis ; den- 
tibus approximatis ; capsulis ovato-oblongis. 
S. Balfouriana (nob.) ; foliis anguste marginatis, remote dentatis ; 
capsulis ovato-cylindraceis. 
This beautiful species of one of the finest genera in the family 
I have sincere pleasure in naming after my highly esteemed 
friend Dr. Balfour, Professor of Botany in the University of 
Edinburgh. 
EXPLANATION OF PLATE XVII. 
Fiq. 1. S. Balfouriana, nat. size. 
Fig. 2. Leaf. 
Fig. 3. Margin of the leaf of S. Reinwardtii. 
Fig. 4. Ditto of that of S. Balfouriana. 
Fig. 5. Perichsetial leaves and capsule. 
Fig. 6. Peristome. — Figs. 2-6 all magnified. 
XXXV. — Notice of two new species of Ferns belonging to the 
genera Oleandra and Polypodium. By 11. K. Greville, LL.D. 
&c.* * 
[With a Plate.] 
The genus Oleandra of Cavanilles, adopted by Presl and now 
generally received for a section of the old genus Aspidium, is one 
* Read before the Botanical Society of Edinburgh, March 9, 1818. 
