INTRODUCTION. xvii 



kind of lattice-work. The numerous and delicate forms, as well 

 as the perfect regularity and the rich colouring of the peristome 

 render this organ a most beautiful microscopic object. The 

 teeth are strongly hygroscopic, usually, when mature, spreading 

 more or less widely in the dry state, but rapidly converging so as 

 to close the mouth of the capsule when moistened, or even when 

 merely breathed upon. 



The wall of the capsule frequently exhibits stomata, usually 

 not very numerous, and as a rule arranged more or less distinctly 

 in one or two rings round the capsule most commonly towards its 

 base or upon its " neck," i.e., the portion intermediate between the 

 seta and the base of the spore-sac, or inner membrane 

 containing the spores, which as a rule does not reach quite so 

 low as the base of the outer case. The stomata are sometimes 

 superficial, i.e., on the surface of the wall of the capsule (Tab. V. i), 

 sometimes immersed, i.e., sunk in its substance (Tab. V. 2). This 

 distinction is of great importance in the genus Orthotrichum, in 

 which both forms of stomata occur, and afford a safe and useful 

 character for the separation of species and even of groups of 

 species. 



II. CLASSIFICATION, NOMENCLATURE, ETC. 



The primary object of this work being to simplify the 

 determination of our British mosses for the student, and to make 

 it available, as far as possible, for a beginner, it has been my 

 chief aim throughout to introduce as little novelty and to employ 

 as few technicalities as appeared compatible with accuracy and 

 clearness. For this reason I have preferred to keep as closely as 

 possible to the system of classification which prevails in the 

 greater number of those works which the student is most likely, 

 at the outset, to consult, and of which that employed in the 

 second edition of Schimper's Synopsis Muscorum Europseorum 

 may be looked upon as the basis. The researches and critical 

 writings of recent bryologists have added much to our knowledge, 

 and have led to the proposition of new schemes of classification ; 

 but great as was the temptation to follow, more or less closely, on 

 these new lines, it appeared to me that the difficulties put in the 

 way of the student, in a more or less elementary work, by a novel 

 classification and order, were likely to outweigh the advantages 

 they might confer. 



