BBYOPHYTA. 



151 



of trees. Besides the sexual reproduction by means of 



archegonia and antheridia, they 



multiply extensively in a non-sexual 



manner ; namely, by the production 



of peculiar buds, called gemmce 



(Fig. 263, gem). These, in the 



common Liverwort (Marchantia), 



are little cellular bodies, developed 



in cups, ou the upper surface of 



the thallus. When the gemmae are 



full-grown, they fall to the ground, 



and grow directly into new plants. 



The stomates in these plants are 



not of the ordinary kind found in higher groups ; instead 



of being surrounded, as there, by two guard-cells, there are 



sixteen (or more) cells, in four (or more) superposed layers, 



encircling the orifice, which leads into a large air-cavity 



below the epidermis. In this cavity are branching rows 



of cells, which contain the chlorophyll-masses (Fig. 264). 

 2. Musci. This group includes the Sphagnums and 



the true Mosses. The plants (Fig. 262) have stems, 



with sessile leaves and articu- 

 lated root-hairs, or rhizoids ; the 

 leaves are composed of a single 

 layer of cells, and may, or may 

 not, have a midrib. The stems 

 may have an outer, thickened 

 layer, or layers (imperfect scle- 

 renchyma) ; and within, either 



simply thin-walled parenchyma, or an axial bundle of 



very narrow, thin-walled cells — imperfect fibro-vascular 



Fig. 263. A portion of a Liverwort, with the gemmae in cup-like cavities. Fig. 

 264. Section of a frond of Liverwort, showing the stomate (si) and the air-cavity 

 (a) below, containing the cells which have the chlorophyll (cM). 



