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



capsule as the next generation, and singular as it appears, the 

 moss capsule attached to the parent, and seeming only like its 

 fruit, is of a far higher organisation, and exhibits many of the 

 characteristics of the very highest plants. At a mere glance we 

 see a much more considerable differentiation of tissues than the 

 moss can boast of. In the centre there is a white large-celled 

 mass, the columella, corresponding to the colourless inner tissue 

 of the flowering plants ; then there is the ring of spore-producing 

 tissue. Outside this is an air space, crossed by alga-like threads 

 containing chlorophyll, joining on the outside the sub-epidermal 

 tissue, and finally a strongly developed epidermis, in many mosses 

 containing stomata not differing from those of the Phanerogams. 

 These are most remarkable, considering the position the mosses 

 occupy. But again, the non-sexual spores from this complicated 

 organism give rise only to the simple protonema and the almost 

 entirely cellular leafy stem with which we started. But if it is 

 true that the highest development only results from sexual repro- 

 duction, the converse is equally true ; and hence in the most highly 

 developed plants we find sexual reproduction has become empha- 

 sised, as it were, whilst reproduction by means of spores is so 

 obscured that on a superficial view it appears to be absent. 

 Again, in the plants less highly developed than the Bryophyta — 

 namely, the Algae and Fungi — the non-sexual reproduction is 

 paramount, while the sexual is pushed aside till it is often most 

 ditficult to detect. Thus the mosses and the ferns display in their 

 alternation of generations a typical representation of the methods 

 of reproduction in the whole vegetable kingdom. In them the 

 two phases, the sexual and the non-sexual, are balanced ; neither 

 is developed at the expense of the other, and the importance 

 which belongs to them in this respect as an indication of the 

 processes which occur in the other divisions can hardly be 

 overrated. 



Journ. Quekett Microscopical Club, Ser. 2, Vol. X., No. 60, April 1907. 



