323 



stomium, 1 would beg attention to the follovYing particulars: — The teeth, as 

 they are called, occupy one or more whorls ; they are evidently not mere 

 lacerations of a membrane, because they are in a constant and regular num- 

 ber in each genus, and that number is universally some multiple of 4, as 

 the floral leaves of flowering plants are ordinarily of 3, 4, or 5 ; they have the 

 power of contracting an adhesion with each other by their contiguous mar- 

 gins, as the floral leaves of flowering plants; they alter their position from 

 being inflexed with their points to the axis, to being recurved with their points 

 turned outwards, — exactly what happens in flowering plants; the teeth of 

 the inner peristomium often alternate with those of the outer, thus conform- 

 ing to the law of alternation prevalent in the floral leaves of flowering plants; 

 and, finally, if we compare the various states of the leaves of Buxbaumia 

 aphylla with the teeth of Mosses, it is impossible not to be struck with the 

 great similarity in the anatomical structure of the two. These are the con- 

 siderations which have led me to the conclusion, that the calyptra, the oper- 

 culum, and the teeth of Mosses, are all modified leaves ; and hence that the 

 theca is to be considered more analogous to a flower than to a seed-vessel. 

 With regard to the membrane, or epiphragma, which occasionally closes up 

 the orifice of the theca, it may be considered as formed by the absolute cohe- 

 sion of the leaves of the peristomhim, just as the operculum of Eudesmia is 

 formed by the cohesion of the petals ; and this is confirmed, first, by Ca- 

 lymperes, in which the membrane ultimately separates into teeth, and by the 

 fact that the horizontal membrane exists most perfectly in such genera as 

 Polytrichum and Lyellia, in which there is no distinct peristomium. It now 

 remains to explain the internal structure of the theca consistently with the 

 theory that has been advanced of the peristomium, operculum, and calyptra. 

 I consider the theca to be merely the thickened apex of the axis, the sporules 

 to be a partial dissolution of its cellular tissue, and the columella to be the" 

 unconverted centre. That the end of the axis of plants frequently becomes 

 much more incrassated than the theca of Mosses, requires no illustration 

 for those who are acquainted with the spongy receptacle of Nelumbium, 

 Rubus, and Fragraria, the dilated disk of Ochna, the curious genus Esch- 

 scholtzia, or Rosa, or Calycanthus, or, finally, the spadix of Arums. That 

 the tissue is frequently separated by nature for particular purposes, is proved 

 by the production of pollen out of the cellular tissue of an anther, and by 

 the general law of propagation that seems to prevail in flowerless plants, as 

 Ferns, Lichens, Algse, and Fungi; the same phenomenon may be therefore 

 expected in Mosses. That the columella should be left in this dissolution 

 of the tissue might be expected, from its being a continuation of the seta 

 or axis of developement, the tissue of which is more compact, and 

 of course less liable to separation, than the looser tissue that surrounds it; 

 this is analogous to the separation of the pollen from the connectivum of 

 most plants, or from parts only of the anther of all those genera which, 

 like Viscum, ^giceras, or Rafflesia, have what are called cellular anthers ; 

 and to the very common separation of the placenta, or a portion of it, 

 from the dissepiments, as in Bignoniaceee, Ericese, and many others. That 

 it is presumptuous in me, who lay no claim to reputation as a Cryptogamic 

 botanist, to ofter any opinion upon plants I have only oc(;asionally studied, 

 I am fully sensible; but I hope for the indulgence of the skilfid Crypto- 

 gamist, in consideration of this having been the first attempt to call his 

 attention to the inquiry. 



Geography. Mosses are found in all parts of the world where the 

 atmosphere is humid ; but they are far more common in temperate climates 

 than in the tropics. They are among the first vegetables that clothe the soil 

 with verdure in newly-formed countries, and they are the last that disappear 



