2 A MANUAL OF MOSSES 



the thin wall, consisting of but a single layer of sterile cells, is 

 ruptured, thus liberating the mass of fertile cells, each of which 

 immediately develops into a sperm. Each sperm consists of a 

 more or less oval or club-shaped and curved body, always free- 

 swimming by means of two long slender cilia attached at one 

 end of the body. 



The egg is borne in a special organ termed the archego- 

 niuni. The archegonium is usually more or less stalked and is 

 dififerentiated into a swollen basal portion termed the venter, 

 which contains the one fertile egg cell, and the more slender 

 tapering neck terminating the archegonium above and contain- 

 ing an axial row of sterile cells termed the caiml cells, the basal 

 one of which rests directly upon the egg cell. When the 

 archegonium becomes ripe the canal cells break down into a 

 slimy mass of protoplasm, some of which may escape at the 

 tip of the neck. Sperms are attracted in some manner by the 

 slimy protoplasm thus escaping if there is a sufficient film of 

 moisture present so that they may swim about in the peri- 

 chsetium or on the surface of the plant. Having reached the 

 apex of the archegonium the sperms may enter the canal left 

 open by the disintegration of the canal cells and eventually one 

 of the sperms will reach the egg and, unking with it, bring 

 about fertilization. 



After fertilization the egg immediately begins development 

 as the sporophyte but remains enclosed in the venter of the 

 archegonium, which to a considerable extent expands with the 

 development of the young sporophyte but is finally ruptured 

 and usually carried upward on the tip of the sporophyte, where 

 it is then known as the calyptra or hood. The ultimate end of 

 the sporophyte is the production of spores which arise entirely 

 by division of cells and are thus known as asexual cells. The 

 sporophyte is usually almost devoid of chlorophyll and it de- 

 velops at its base an absorbing organ termed the foot through 

 which its food is obtained from the gametophyte. The sporo- 

 phyte usually develops more or less of a stalk which is termed 

 the seta and which bears at the apex a globose to more or less 

 elongated capsule in which the asexual spores form. The 

 method of opening (dehiscence) of the capsule and the struc- 

 tures often associated with the dispersal of the spores are 

 varied and are so characteristic for the various systematic 

 groups and species that the capsule becomes highly important 

 for the correct systematic placing of the plants. 



Of the mosses there are to be distinguished three well- 

 marked Orders known as the Sphagnales, the Andreaeales, and 

 the Bryales. The order Sphagnales comprises the one genus 

 Sphagnum. These mosses are known as Peat Mosses or Bog 

 Mosses, their characteristic habitat being bogs and the mar- 



