82 



.BOTANY 



PART I 



tissue. It is perforated by air-pores (Fig. 95), which resemble in 

 origin the stomata of higher plants. Hairs, in the form of mucilage- 

 secreting papillae or flat leaf -like scales, 

 are of common occurrence. 



A typical stomatal apparatus with two guard 

 cells enclosing a stoma is found, as GOEBEL ( 54 ) has 

 shown in the thallus of the Liverwort, Anthoeeros ; 

 it must be borne in mind that these stomata are 

 mucilage slits and do not contain air. 



A peculiar capillary apparatus serving for the 

 absorption of water occurs in the Bog Mosses 

 (Sphagnaceae). The cortex of the stem consists 

 of three or four layers of empty cells, the walls of 

 which have annular and spiral thickening, and 

 are perforated by round holes ; these readily absorb 

 water. Similar cells lie singly in the leaves, which 

 are only one layer of cells thick, in the meshes of 

 a network of elongated living cells containing 

 chlorophyll. 



Some Liverworts have a strand of elongated cells serving for 

 conduction. This is situated in the midrib of the ribbon-shaped 

 forms. Conducting strands clearly limited from the surrounding 

 tissue are, however, first met with in the Mosses. 



A relatively simply-constructed conducting strand is shown in transverse section 

 in the stem of Mnium undulatum in Fig. 96 I. The most perfect strands of this 



FIG. 94. Diagrammatic representa- 

 tion of the apex ofMetzgeriafurcata 

 in process of branching, viewed 

 from the dorsal side, a, Apical 

 cell of pajent shoot ; b, apical cell 

 of daughter shoot. ( x circa 370. 

 After KNY.) 



FIG. 95. Surface view and transverse section of the thallus of Man-hantia polymorpha. In A, an 

 air-pore, as seen from above; in B, as seen in cross-section ass, assimilating cells, (x 240. 

 After STRASBURGER.) 



kind are found in the steins of the Polytrichaceae. They contain elongated, thin- 

 walled, water-conducting elements, thick-walled mechanical tissue, and elongated 

 cells that contain proteids and starch. Strands of similar construction are also 

 found in the thick midrib of the leaves and are connected with that of the stem. 



