PRELIMINARY OBSERVATIONS. 3 



line to many inches in length, mostly of a clear unsullied 

 green, but sometimes, especially when exposed to the sun, 

 variously shaded with golden brown or different tints of red 

 and purple, in a few cases only being almost devoid of colour, 

 or of a very pale glaucous green. The stems are either erect 

 or more or less inclined, sometimes indeed quite prostrate and 

 closely attached to the soil or substance on which they grow. 

 They are clothed with leaves, or in those cases where, at first 

 sight, they seem absent, as in Buxbaumia aphylla (Plate 19, 

 fig. 6), with rudiments of leaves, which are for the most 

 part symmetrical, and arranged round the axis in definite 

 order, so as to present a more or less cylindrical appearance, 

 or, in a few cases, so disposed as to make the stem or branches 

 of the plants flattened or triangular. These leaves are usually 

 without true stipules or the inflected lobes or sacs which are 

 so common in Jungermannice, though in one or two genera, as 

 Hypopterygium (Berk. Crypt. Bot. fig. 99 d), there are either 

 true stipules, or certain of the leaves assume the form of sti- 

 pules, while in some Homalia* there is an approach to inflected 

 lobes. The habit of Mosses is indeed so peculiar, that when 

 their distinguishing features have been once mastered there is 

 seldom the slightest difficulty in distinguishing them at the 

 first glance, and determining whether a Moss or Liverwort is 

 before us. In those cases where the stem is much flattened, 

 and indeed in all doubtful cases, every difficulty is removed if a 

 single fruit is present, except in the small osculant group 

 of Andreaee, which in their sporangium and colouring approach 

 nearer to Jungermanniw. 



Mosses are naturally divisible, according to their external 

 characters, into two great classes, which have received the 

 names of Acrocarpous and Pleurocarpous, because in the one 

 case, the fruit terminates the stem, and in the latter, it is 



b 2 



