chairn, near Glasgow, a gentleman who, imbibing an early taste 
for botany under the celebrated De Candolle at Geneva, 
has continued to pursue the study vnth. great zeal ; and during 
an excursion which he lately made through the British settle- 
ments at Guaiana, collected a rich and abundant harvest of 
plants. These have been consigned to me, with a liberality 
that demands my warmest acknowledgments, together with nu- 
merous descriptions, made from living individuals, chiefly of 
those belonging to the tribe of Palms. Among his choice col- 
lection, are many specimens of the Fern now under considera- 
tion, in an excellent state of preservation. 
The nature of the capsules of this plant, and their situa- 
tion, require that a new Order in the Class Cryptogamia should 
be established for it, and I have named it after the only genus 
that is at present known to belong to the family. Perhaps its 
place should be near Marsileacece of Brown. 
The East Indian Pteris thalictroides of Swartz and 
WiLLDENOw {Acrostichum, L.), has unquestionably many 
points in common with this plant, and it is equally of aquatic 
origin : but the fructification is nowhere described with suffi- 
cient accuracy to enable me to speak satisfactorily upon the 
point of their affinity, and I have not had the opportunity 
of seeing specimens. I cannot, however, help expressing it as 
my opinion, that P. thalictroides * will rank in the same ge- 
nus with the present subject of our consideration. As a spe- 
cies, it may be distinguished by its having sterile fronds, diffe- 
rent from the fertile ones : whereas in all the specimens of 
Parkeria pteridoides, the fronds are alike. 
Another plant, allied to this, is the Pteris cornuta of Pa- 
LisoT DE Beauvois' Flove d'Oware et de Benin, p. 62. t. 37. 
That author, however, both describes and figures the capsules 
as furnished with an annulus, and having seeds quite different 
from those of Parkeria. This grows in salt-water pools on 
the coast of Africa. 
Mr Parker finds the present fern in fresh-water ditches, 
in the district of Essequibo. 
Fig. 1 . Portion of the frond. Figs. 2. & 4. Under side of a portion. Fig. 3. 
Back view of ditto. Fig. 5. Under side, witli the involucre laid open, 
to shew the situation of the capsules. Fig. 6. Capsules. Fig. 7. Cap- 
sule torn open. Fig. 8. Seeds.— more or less wagnified. 
* This is mentioned by Mr Brown, Prodr. Fl. Nov. Holl. p. 154, as constituting a 
new genus ; and, since the above was printed, I find that, in Fmnkliii's Jouo-nal, Aw. 
under the article Cryptogramma, Mr Brown has called it Teleozoma, and assigns to it 
" Capsulai sessik's, annulo complelo latissimo.'" Hence, however closely these two genera, 
Crgplofframma and Tcleozoma, may be allied to our plant in habit, they are essentially 
ditferent in the structure of the fructification. 
