130 The Microscope. 



the mosses, for the convenience of those who have no previous ex- 

 periei^ce in their study. The more advanced student will have 

 recourse to such works as Bennett and Murray's Cry ptogamic 

 Botany, Bessey's Botany, Strasburger's Vegetable Histology, 

 ■etc., (from which many portions of this paper are taken), for in- 

 formation in regard to the structure and physiology ; and to the 

 Manual of Lesquereux and James as the best available stan- 

 dard in respect to the classification. 



Mosses are found in almost every part of the world from the 

 coldest to the hottest, though they are most abundant in tem- 

 perate regions, where they are everywhere to be found, flourish- 

 ing most luxuriantly in damp localities. They are mostly aerial 

 plants, growing upon moist earth, the trunks of trees, decaying 

 wood, rocks, etc., a few species in water. As is well known, they 

 are small in size, varying from less than aV inch to several inches 

 in height, the usual height being from one to two or three inches. 

 They are generally bright green in color, occasionally whitish or 

 brownish, and all contain chlorophyll. The mature plant con- 

 sists of a leafy stem fixed to the soil or other support by root- 

 hairs or rhizoids — mosses have no true roots. These rhizoids 

 are branched, articulated filaments which spring from the outer 

 layer of cells in the stem, often completely covering its lower 

 portion with a brownish, matted, felt-like mass. The leaves are 

 •small, sessile, varying in shape from linear or narrowly lanceo- 

 late to brpadly ovate or almost orbicular, and usually inserted 

 somewhat obliquely on the stem in two or three straight or spiral 

 rows. They consist generally of a single layer of cells, and are 

 either nerveless or traversed lengthwise by a midrib or costa, in 

 a. few species by two. 



The plants of the class Musci (which includes the Mosses and 

 Liverworts), seem to form a kind of connecting link between 

 the vascular and non-vascular cryptogams. Although they con- 

 tain no true vascular tissues, yet in some genera (^Leucobryum, 

 Barhula, etc.), there is a diff'erentiation of the tissue of the stem 

 into an inner portion, composed of large thin-walled cells, 

 {parenchyma), and an outer portion, consisting of one or more 

 layers of thicker- walled cells, partaking of an epidermal char- 

 acter and forming a kind of imperfect sclerenchyma. In other 

 genera (e. g. Fanaria, Mnium, etc.), the differentiation of structure 

 is still more evident. If we make a cross-section of the stem of 



