I50 



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 fiUform 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. :59.— Tran 

 single cells of tlie 



:rse section of tlie stem of Bryitm 

 :-hairs produced by the outgrowth 

 itermost layer. 



Fig. is^b.—Fiinaria hyoroiiietyfca. .1 a small leafy 

 shoot {g) with the calyptra (r) ; B a plant (g) with the 

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

 calyptra; Ca longitudinal section through the middle of 

 the capsule; (/operculum; a annulus ;/ peristome ; c c' 

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

 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 INIoss 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-Hke 

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

 lower side, as well as leaf-like 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- 



