150 



■LECTURE IX. 



of tissue, chiefly parenchymatous fundamental tissue, and which is generally 

 differentiated into a compact colourless portion, and chlorophyll-tissue traversed 

 with numerous intercellular spaces. Of special interest in this respect is the 

 segmenting off of a portion of the epidermis as the deciduous cover of the 

 moss-fruit, and, in the more highly organised forms, the formation of the so-called 

 peristome. This consists of four, eight, sixteen or more so-called teeth, which on 

 their part arise from peculiarly differentiated rows of cells beneath the cover mentioned, 

 by the strong thickening and lignification of the cell-walls : this is illustrated in 

 part by Fig. 122, and the accompanying Fig. 160. It has been already pointed 

 out that in the filiform thin shoot-axis of the true Mosses, a strand, consisting of 

 narrow, elongated cells, and which is undoubtedly to be regarded as a rudimentary 

 vascular bundle, runs within a well-marked fundamental tissue, which is surrounded 



FIG. 139. — Transverse section of tlie stem of Bryum 

 foseum (X go), m root-hairs produced by tlie outgrowth 

 of single cells of the outermost layer. 



Fig. 159*. — Fiijiaria hygrometrica. A a small leafy 

 shoot {^) with the calyptra (c) ; B & plant \g) with the 

 almost ripe sporogonium ; s the seta ; /the capsule ; c the 

 calyptra ; C a longitudinal section through the middle of 

 the capsule; (^operculum; ^ annulus ;./ peristome ; c i^ 

 columella ; h air cavity ; s mother-cells of spores. At / 

 the loose tissue of the columella presents the appearance 

 of confervoid filaments. 



by a more or less sharply defined epidermal layer; and when the leaves of the 

 Moss, elsewhere consisting of a simple cell-layer, possess a mid-rib, in this also 

 a rudimentary vascular bundle runs, joining that of the shoot-axis. Since the 

 roots of the Moss only consist of jointed cell-filaments, such tissue differentiations 

 obviously cannot exist in them. • 



Much simpler are the forms assumed by the tissues in the majority of the 

 Liverworts; which, however, in their most highly organised forms, the Marchantiae, 

 nevertheless attain a very considerable degree of organisation. The ribband-like 

 foliar shoots of these plants, lying flat on the substratum, produce root-hairs on the 

 lower side, as well as leaf-lijie outgrowths ; while the upper side of the shoot developes 

 into an organ of assimilation. A sharply marked epidermis invests an inner 

 mass of tissue consisting of several layers, which is to be distinguished as funda- 



