184 BOTANY. 
an upper and an under one, the latter bearing the root- 
hairs (rhizoids), by means of which the plant is fixed to 
the ground. Jn this class breathing-pores are found for 
the first time in the vegetable kingdom. They are of very 
simple structure (Fig. 101). 
386. The leaves, when present, are usually in two rows 
(sometimes three), and are either opposite or alternate. 
The tissues of the plant-body show a little differentiation; 
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and 8, ripened and split, spore-fruit. . 
the leaves, however, have no midrib or other veins, and 
consist of a single layer of cells. The development of the 
stem is always from a single apical cell, which repeatedly 
divides. 
387. The asexual reproduction of Liverworts takes place 
by means of peculiar bodies, the buds (or gemme) so fre- 
quently to be seen in the Common Liverwort (Marchantia 
polymorpha). In the latter plant they are little stalked 
