4 J. BURTON ON THE REPRODUCTION OF MOSSES AND FERNS. 



moss, whilst the upper finally develops into what is known as the 

 capsule. In the capsule a ring of tissue is differentiated, which 

 gives rise to the mother-cells of the spores. The archegonium 

 for some time grows with the capsule, but at last the lengthening 

 stalk tears it at the base, when it is carried up and forms the 

 " calyptra," the outermost covering of the capsule. Under the 

 calyptra there is a kind of lid — the " operculum " — and below that, 

 surrounding the mouth of the capsule, there is, in many species, 

 a peristome composed of variously arranged teeth, whose purpose 

 is subservient to the dissemination of the spores. The base of the 

 embryo penetrates the tissue of the upper part of the stem of the 

 parent, but probably the stem grows up round it also. It is from 

 this source that the moss capsule derives part of its nourishment ; 

 it has no root of its own, and no separate existence apart from its 

 parent. Although generally regarded as being merely the fruit, 

 it is in reality, as I have endeavoured to show, a second genera- 

 tion, derived from the fertilised germ -cell borne by the original 

 moss plant. At the same time, although it is usually described 

 as parasitic upon its parent, it is only very partially so, and from 

 its structure (to be again referred to) is obviously able to obtain 

 its carbon directly from the air, as well as any other plant. The 

 capsule is called a " sporophyte," because, regarded as a separate 

 individual, it produces spores, these being non-sexual reproductive 

 bodies, containing no embryo, but having an outer somewhat 

 tough coat and an inner thin one, and filled with protoplasm, 

 some oil and chlorophyll. On the commencement of growth the 

 outer skin is burst, and the inner, protruding, at one part forms a 

 rudimentary root, and opposite to that a much-branched structure, 

 inmost species resembling some of the common filamentous algae. 

 It is composed of numerous cells, contains abundant chlorophyll, 

 and is called a " protonema." After a time some of the branches of 

 the protonema produce buds, from which roots spring and take 

 a downward direction, while a stem grows upwards and forms 

 leaves, becoming a moss plant identical with that from which we 

 started. Thus, to complete the life-cycle, the so-called alternation 

 of generations, three stages are necessary, — (1) the moss plant 

 which bears the sexual reproductive organs ; (2) the capsule 

 produced by these, which, though living on the parent, is 

 really the next generation : this forms non-sexual spores, which 

 give rise to (3) the protonema, on which arise as branches 

 (not as a separate organism) the leafy stems with which we 

 started. 



