QQ BRYACE^. [AcROGENs. 



peristomium often alternate with those of the outer, thus conforming 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 other Urn- 

 mosses, it is impossible not to be struck with the great similarity in the anatomical 

 structure of the two. These considerations led me to the conclusion, that the cal;y^tra, 

 operculum, and teeth of Urnmosses, are all modified leaves ; and hence that the spore- 

 case 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 spore- 

 case, it may be considered as formed by the absolute cohesion of the leaves of the peri- 

 stome, just as the operculum of the genus Eudesmia is formed by the cohesion of petals ; 

 and this is confirmed, first, by Calymperes, 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 Lyelha, m which there is no distinct peristome. As to the 

 internal sti'ucture of this cm-ious apparatus we may regard the spore-case as the hollow 

 apex of the axis, the sporules as a partial dissolution of its cellular tissue, and the 

 columella as the unconverted centre. That the end of the axis or growing point of plants 

 frequently becomes much more thickened than the spore-case of Urnmosses, requires 

 no illustration for those who are acquainted with Eschscholtzia, Rosa, or Calycanthus. 

 That tissue is frequently disintegrated for particular pm'poses, is proved by the produc- 

 tion of pollen out of the cellular tissue of an anther, and by the general law of propaga- 

 tion that seems to prevail in all the lower alliances of plants ; the same phenomenon 

 may be therefore expected m Urnmosses. 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 development, 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 connective of most plants, or from parts only of the anther of all 

 those genera which, hke Viscum, ^giceras, or Raflflesia, have what are called cellular 

 anthers. 



Mr. E. Quekett has lately proved the general accuracy of these \aews by the discovery 

 of a monstrous moss, in which common leaves take the place of the spore-case, its peristome, 

 and other appai-atus. As this is a very curious subject, I extract at length his observa- 

 tions, with a few miimportant omissions : — " Soon after Mr. Ward made known his plan 

 of growing plants in closely-glazed cases I had constructed a small case, in which were 

 placed various Mosses, both in fruit, and havmg the tendency to form fruit. Among 

 the number was a mass of Tortula fallax, showing, at the tune, the early condition of 

 the seta, capped with a calyptra. After Avatching the progress of the plants, it was dis- 

 covered that the Tortula, which, when placed in it, showed every tendency to produce 

 fruit, now presented, instead of fruit advancmg to matm-ity, a miniature foi'est of 

 elevated stems, leafy above and below, but in the mtermediate portion, destitute of 

 leaves ; in fact, all appeai'ance of capsules approaching matvu-ity was dissipated. On 

 placing some of the plants under the microscope, it was evident that the specimens were 

 furnished with the usual leaves at the base of the plant, — the seta existed, and presented 

 the usual broAvm colour, quite destitute of leaves, but m the place of the capsule, there 

 was a continued elongation of the seta, of a gi*een colour, bearmg several green leaves, 

 varymg in number in different specimens, being generally from about twelve to twenty. 

 It appears that the capsule had scarcely commenced to be formed, when the elements 

 of the modified leaves, (which I conceive would have otherwise formed the capsule and 

 peristome), havmg received an increased degree of heat, combined A\-ith more moisture 

 than is natm'al to these plants, occasioned by the structure of the case, and by its posi- 

 tion, instead of bemg converted into the ordmary capsule and peristome, the matters 

 which entered the plants were not appropriated to the development of organs of repro- 

 duction, but imderweut a change into a state fitting them apparently for the purposes 

 of nutrition." 



Mr. Quekett objects, however, to that part of the theory which assumes the spore-case 

 to be the hollowed apex of the axis ; he considers the theca and operculum to be the 

 representatives of a consolidated calyx ; the corolla to be the Hnmg membrane, whose 

 fringed edge constitutes a peristome, which is either smgle or double, and appears to be 

 the representative of the reproductive apparatus ; and the columella to be the recep- 

 tacle, torus or axis on wliich these several organs are arranged. 



Fine illustrations of the Anatomy of Urnmosses will be found in Link's Ausgew. 

 Anat. Bot. Ahhild. Fasc. 4. 



Urnmosses are fotmd 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 verdm'e in newly-formed eoimtries, and 

 they are the last that disappear when the atmosphere ceases to be capable of nomish- 

 ing vegetation. The first green crust upon the cinders of Ascension consisted of minute 



