is always conspicuously notched. There is a prominent midrib extending along the center of each branch of the thallus. On the under side of the thallus, especially along the midrib, there are numerous rhizoids which serve the purpose of roots, absorbing nourishment from the earth and holding the plant in its place. The upper surface of the thallus is divided into minute rhombic areas that can be seen with the naked eye. Each of these areas is perforated by a small breathing pore or stomate that leads into a cavity just beneath the epidermis. This space is surrounded by chlorophyll-bearing cells, some of which stand in rows from the bottom of the cavity (Fig. 290). The delicate assimilating tissue is thus brought in close communication with the outer air through the pore in the thick, protecting epidermis.
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Fig. 290. — Section of Thallus of Marchantia. Stomate at a.
At various points on the midrib are little cups containing
small green bodies. These bodies are buds or gemmæ which are
outgrowths from the cells at the bottom of the cup. They become
loosened and are then dispersed by the rain to other places, where
they take root and grow into new plants.
The most striking organs on the thallus of marchantia are the peculiar stalked bodies shown in Figs. 288, 289. These are termed archegoniophores and antheridiophores or receptacles. Their structure and function are very interesting, but their parts are so minute that they can be studied only with the aid of a microscope magnifying from 100 to 400 times. Enlarged drawings will guide the pupil.
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Fig. 291.—Section through Antheridiophore of Marchantia, showing antheridia. One antheridium more magnified.
The antheridiophores are fleshy, lobed disks borne on short stalks
(Fig. 291). The upper surface of the disk shows openings scarcely
visible to the naked eye. However, a section of the disk, such as
is drawn in Fig. 291, shows that the pores lead into oblong cavi-
