222 
ORGANOGRAPHY. 
BOOK I. 
stomates; and Von Martius, in certain membranes enclos- 
ing the spiral vessels. None of these opinions are now 
adopted. 
In Ophioglosseae, a remarkable tribe of ferns, the fertile 
leaf is rolled up in two lines parallel with its axis or midrib, 
and at matm'ity opens regularly by transverse valves along 
its whole length, emitting a fine powder, which, when magni- 
fied, is found to consist of particles of the same nature as the 
sporules found in the thecae of other ferns ; here there are no 
thecae, the metamorphosed frond probably performing their 
functions. Such is my view of the structure of Ophioglosseae ; 
but by other botanists it is described as a dense spike of two- 
valved capsules, dehiscing transversely. 
2. EquisetacecB. 
In these plants, which may, perhaps, be more properly con- 
sidered the lowest form of flowering plants, the organs of 
reproduction are arranged in a cone, consisting of scales 
bearing on their lower surface an assemblage of cases, called 
theccB, follicidi, or involucra, which dehisce longitudinally in- 
wards. In these thecae are contained two sorts of granules ; 
the one very minute and lying irregularly among a larger 
kind, each of which is wapped in two filaments, fixed by their 
middle, rolled spirally, having either extremity thickened, and 
uncoiling with elasticity. By Hedwig the apex of the larger 
granules was supposed to be a stigma, and the thickened ends 
of the filaments anthers, the small granules being the pollen. 
At any rate it is certain that the larger granules, round which 
the elastic filaments are coiled, are the reproductive particles. 
3. LycojJodiacecB. 
These are leafy plants with the habit of gigantic mosses. 
Their leaves and stem have the same structure as those plants, 
except that the former are sometimes provided with stomates, 
and the latter with vessels. Their organs of reproduction 
are of two kinds : the one kidney-shaped two-valved cases, 
called theccE^ conceptacles^ or capsules, destitute of internal 
divisions, and filled with minute powder-like granules, which, 
in consequence of lateral compression, from being spherical, 
