311 



ovulum, and the 4 swollen filajiients that surround it 4 grains of pollen 

 united in pairs to the base of the ovulum. It is probable that the nearest 

 approach to the structure of sexual organs does take place here, and 

 that, considering the analogy between the thecae of Equisetum and the lobes 

 of the anther of ConiferjE, and the filaments of the former and the quaternary 

 grains of pollen of Cycas, the parallel drawn by M. Brongniart is just; but 

 it must, at the same time, I think, be admitted, that it is very doubtful whe- 

 ther, in this order, the parts are any thing more than representatives of the 

 sexual a,pparatus, without the power of performing its functions. 



The germination of the sporules has been explained, both by Agardh and 

 BischofF. The former (^p/« or. 120) describes it thus: From 3 to 14 days 

 after they are sown, they send down a filiform, hyaline, somewhat clavate, 

 simple root, and protrude a confervoid, cylindrical, obtuse, articulated, toru- 

 lose thread, either 2-lobed (in E. pratense) at the apex, or simple (in E. pa- 

 lustre). Some days after, several branches grow out and are agglutinated 

 together, forming a body resembling a bundle of confervoid threads, each of 

 which pushes out its own root. The account of BischofF (iVo v. Act. Acad. 

 N. Cur. 14. t. 44.) is not .materially different : he finds the confervoid 

 threads or numerous processes of cellular developement go on growing and 

 combining, until a considerable cellular mass is formed ; then this mode of 

 developement ceases, and a young bud is created, which -springs up in the 

 form of the stem of the Equisetum, at once completely organised, with its 

 air-cells, its central cavity, and its sheaths, the first of which is formed be- 

 fore the elongation of the stem, out of the original cellular matter. 



Geography. From the researches of M. A. Brongniart, it appears 

 indisputable that plants very nearly the same as these in their organisation 

 formed part, and a considerable part too, of the original 'vegetation of the 

 globe ; not, however, puny species, such as those of our days, with feeble 

 stems,, scarcely ever exceeding 3 or 4 feet in height, but gigantic vegetables, 

 many yards long. If, indeed, certain striated fossils of the coal fields 

 should be referable to this family, it will be found that some of them must 

 have been vast trees. In our days they are found in ditches and rivers in 

 most parts of the world, within and without the tropics; they have not, how- 

 ever, been yet seen in New Holland. 



Properties. None of importance in a medicinal point of view;- they 

 are said to be slightly astringent and stimulating, and have even been recom- 

 mended as diuretics and emmenagogues ; they arCj however, not now em- 

 ployed. In economical purposes they are found highly useful, for polishing 

 furniture and household utensils ; a property which is due to the presence of 

 a great quantity of silex below their cuticle. According to the observations 

 of Dr. John of Berlin, they contain full 13 per cent of siliceous earth. 

 Ed. P. J. 2. 394. The ashes have been found by chemists to contain half 

 their weight of silica. Jameson s Journal, Jem. \830,y>- 101. The quantity 

 of silex contained beneath the cuticle of Equisetum hyemale is so great, that 

 Mr. Sivright succeeded in removing the vegetable matter and retaining the 

 form. Grev. Fl. Edin. 214. On subjecting a portion of the cuticle of 

 Equisetum hyemale to the analysis of polarised light under a high magnify- 

 ing power. Dr. Brewster detected a beautiful arrangement of the siliceous 

 particles, which are distributed in two lines parallel to the axis of the stem, 

 and extending over the whole surface. The greater number of the particles 

 form simple straight lines, but the rest are grouped into oval forms connected 

 • together like the jewels of a necklace, by a chain of particles forming a sort 

 of curvilinear quadrangle, these rows of oval combinations being arranged in 

 pairs. Many of those particles which form the straight lines do not exceed 

 the 500th of an inch in diameter. Dr. Brewster also observed the remark- 



