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The third group, to which he should confine himself, is the Bryince. These 

 are the frondose, or true mosses. 



The true mosses number some 8,000 or 9,000 species, and they naturally 

 fall into two divisions, which are readily known with a little practice, and 

 are very convenient for the purpose of classification. 



1. Acrocarjri. 



2. Pleurocarjn. 



The acrocarpi have the fruit rising from the termination of the stem, as in 

 the well-known Polytrichum commune. 



The pleurocarpi are branched laterally, and have the fruit rising from 

 the side, as in Hypnnm. 



In earlier times the mosses were divided by the peristome or fringe round 

 the month of the capsule, and it was considered only necessary to count the 

 teeth, or see if the capsnle did not open, thus forming a very convenient 

 number of genera, but bringing together the most heterogeneous species. 



The first writer to make an alteration in the classification was his friend 

 Dr. Spruce, the famous South American traveller, in his work on the mosses 

 of the Pyrenees in 1848. He published his ideas that the cleistocarpi, the 

 capsules of which never open, but merely crumble to pieces, and the 

 gymnostomi, or those with a naked mouth to the capsnle, were merely less 

 perfectly developed individuals of higher genera, and therefore should no 

 longer be retained as separate genera of mosses. This was followed up by 

 other great bryologists, and it is undoubtedly the most philosophical way of 

 viewing the subject. 



Among the acrocarpi we get one genus Andrewa, which has the capsule 

 splitting at the side into four or eight valves, the capsule not opening at the 

 top or bottom. This constitutes the section Schistocaripi, or split fruited 

 mosses. 



It is a great advantage to divide off species which have well defined 

 characteristics, and this the valvular fruit enables us to do with the 

 Schistoca?yn, although by the leaves they are allied to Grimmia. 



The fruit of all the great bulk of the mosses is stegocarporous, or provided 

 with a lid, which is thrown off to give exit to the spores, and only in a few 

 cases do we find the lid wanting, and the spores obtaining freedom by the 

 decay of the capsule wall ; these are termed the Cleistocarpi, which minute 

 mosses are undoubtedly low conditions of more highly organized families. 

 In some cases a lid is present, although it never separates at all, which is 

 one step above the lowest form seen in Ephemeriun. 



In the higher mosses we get two very distinct forms of peristome, one the 

 JVematoclontes, characteristic of the Polytrichum family, and a few other 

 allied mosses. The Polytrichum has teeth with threads from the top of one 

 tooth through the base up into the next, and each tooth consists entirely 

 of these threads united by cellular material, and fixed to the drum-like head 

 of the columella. 



The other great group is ArtJwodontes, or jointed tooth mosses. These 

 joints enable the teeth to bend in and out, giving them the beautiful 

 hygroscopic character common to them, closing in wet weather and opening 



