222 ORGANOGRAPHY. BOOK I. 



stomates; and Von Martins, 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 maturity 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, peihaps, 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, JhllicuH, 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 lax'ger 

 kind, each of which is wi'apped 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. Lycopodiaceos. 



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, conceptades, or capsules, destitute of interna 

 divisions, and filled with minute powder-like granules, which, 

 in consequence of lateral compression, from being spherical, 



