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construction of every organ of plants, except thi 3tem out of modified leaves, 

 seemed to be deviated from in the Cryptogamic class generally, and in Mosses 

 in particular. An uninitiated person, reading the definition of a genus of 

 Mosses, might suppose that it was in that tribe that the approach to the ani- 

 mal creation, of which so much has been said, takes place. Unacquainted with 

 the exact meaning of the Latin words employed by Cryologists, he might un- 

 derstand by the peristomium a jaw, by the calyptra a nightcap, and by the 

 struma a kind of goitre ; and when he saw that teeth belonged to this jaw, he 

 would naturally conclude that it was really a vegeto-animal of which he was 

 reading. Struck with the evident absurdity of giving such names to parts of 

 plants, without at the same time explaining their real nature, I ventured to call 

 the attention of naturalists to the subject by the following paragraph in the lit- 

 tle book above referred to. 



"539. The calyptra may be understood to be a convolute leaf; the opercu- 

 lum another; the peristomium one or more whorls of minute flat leaves; and 

 the theca itself to be the excavated distended apex of the stalk, the cellular 

 substance of which separates in the form of sporules." 



It is now time to show upon what evidence and reasoning this hypothesis 

 may be sustained. Every one agrees in describing tire calyptra as a membrane 

 arising from between the leaves and the base of the young theca, and as en- 

 veloping the latter, but having no organic connexion with it : when the stalk 

 of the theca lengthens, no corresponding extension of the parts of the calyptra 

 takes place; so that it must be either ruptured at its apex (as in Jungermannia), 

 or at the base ; and in the latter case it would necessarily be carried up upon 

 the tip of the theca, which it originally enveloped. Now, what can be more 

 reasonable than that such an organ, situated as I have described it to be, should 

 be one of the last convolute' leaves of the axis which the theca terminates, 

 bearing the same relation to the latter as the convolute bractea to the flower of 

 Magnolia, or, to speak more precisely still, as the calyptriform bractea^ to the 

 flower of Pileanthus 1 If the calyptra be anatomically examined, especially 

 in such genera as Tortula and Dicranum, no difference in its tissue and that of 

 the leaves will be observable ; and that very common tendency to dehisce on 

 one side only as the diameter of the theca increases, which characterizes the 

 dimidiate calyptra, may not unreasonably be understood to be the separation at 

 the line where the margins of the supposed leaf united ; in the mitriform ca- 

 lyptra this separation at a given line does not take place, and the consequence 

 is an irregular laceration of its base. The analogy of the calyptra being of this 

 nature, the next inference would naturally be, that the part it contains is analo- 

 gous to a flower-bud. Upon this supposition, the external series of parts belong- 

 ing to this supposed bud would be the operculum ; the adhesion of this to the 

 theca, which would answer to the apex of the axis, or to the tube of the calyx of 

 flowering plants, would be analogous to that which obtains in Eucalyptus, or per- 

 haps more exactly to that of Eschscholtzia ; but it would remain to determine of 

 how many parts, in a state of cohesion, it was made up. In the paragraph 

 above quoted, it is stated to be one only ; but I confess I have no better reason 

 to offer for this than the absence of any trace of division upon its surface or in 

 the substance of its tissue, and also perhaps the apparent identity of nature be- 

 tween it and the calyptra when both are young, in (he Tori ula and Dicranum 

 genera already cited. With regard to the peristomium, 1 would beg attention 

 to the following 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 number in each genus, and that number is 

 universally some multiple of 4, as the floral leaves of flowering plants are ordi- 

 narily of 3, 4, or 5 ; they have the power of contracting an adhesion with each 

 other by their contiguous margins, as the floral leaves of flowering plants ; they 



