16 



rounds the mouth of the capsule regulating the dispersion of the 

 spores. In its complete form it consists of an inner aud an outer 

 row of teeth, the outer row being rather stouter, darker coloured, 

 and entire, while the inner row is more delicate and is frequently 

 supplemented by fine cilia. The long twisted peristome of Bar- 

 bula is a very beautiful object and readily observed as one species, 

 Barbula muralis, is abundant on walls everywhere. 



Interesting peristomes are also found in the Genera Bryum, 

 Polytrichum, and Fontinalis and their examination is often of 

 great value for purposes of classification. Although the capsule 

 is generally parasitic on the moss plant, it occasionally contains 

 abundant chlorophyll and is provided with stomata which never 

 occur in the leaves. The assimilative functions are generally 

 carried on at the base of the capsule known as the apophysis, 

 which reaches an extraordinary development in the genus 

 Splachnum, where it consists of a large spherical or pear-shaped 

 mass of tissue provided with numerous stomata which might be 

 mistaken for the true capsule, which is very small. 



Besides the normal method of reproduction by spores, mosses 

 are also frequently reproduced directly from the moss-plant of 

 the first generation by means of vatiously shaped reproductive 

 bodies known as gemmge, which are produced on various parts of 

 the plant and are often very characteristic of different species ; 

 Tetraphis pellucida, which is very abundant on the Sussex sand- 

 rocks, affords a very interesting example of this method of repro- 

 duction. 



Nearly 600 species of the true mosses are found in the British 

 Isles of which upwards of 300 have been recorded for Sussex, 

 which, with the varied conditions it affords, is an excellent county 

 for mosses. 



The theory of an alternation of generation in the life history 

 of a moss has been referred to so it is perhaps only just to observe 

 that it has recently been called in question, at least in its extreme 

 form. A question at present interesting botanists in connection 

 with it being, whether the spore-bearing plant or capsule and the 

 oophyte or sexual moss-plant are homologous with one another or 

 whether the capsule is an entirely new formation intercalated io 

 the life history, or, as it is called, antithetic to the sexual plant. 

 According to the antithetic view all the vegetative parts of the 

 capsule have arizen from the sterilization of tissue which might 

 have produced spores, e.g. the wall of the capsule, the apophysis, 

 where present, the seta, peristome, etc., have been produced by 

 the metamorphosis of spore- forming cells. 



In connection with this view the capsule of Nanomitrium, 



