The organs of reproduction are very conspicuous by their colour and form. They are always situated on the leaves, the plants being very frequently monœcious. The antheridia (Fig. 61 _B_, _a_) are modified leaflets or the terminal cell of a leaf; they are spherical and become red when mature. Their wall consists of 8 “shields,” _i.e._ of plate-like cells, 4 of which cover the upper half, and are triangular; the 4 round the lower half, to which the stalk of the antheridia is attached, being quadrilateral, with sides of unequal length. The shields (Fig. 61 _C_) have dentated edges, with the teeth fitting into one another, and their faces ornamented with ridges. From the centre of the internal face of each shield (_C_) a cylindrical cell, the _manubrium_, projects nearly as far as the centre of the antheridium; at the inner end of each of the manubria a spherical cell, the _capitulum_, is situated. Each capitulum bears six secondary capitula, from each of which four long coiled filaments (_C_, _D_) project into the cavity of the antheridium. These filaments are divided by transverse walls into from 100–200 discoid cells, in each of which a biciliated, coiled spermatozoid is developed (_D_, _E_) from the nucleus. The spermatozoids escape from their mother-cell and are set free by the shields separating from one other. The female organ of reproduction (Fig. 61 _B_, 63) is a small modified shoot, whose apical cell functions as an oogonium, its protoplasm forming the oosphere, which has a colourless receptive-spot at the summit (Fig. 63 _u_). The oogonium is situated on a nodal cell, from which 5 cells grow out in a circle and coil round the oogonium, covering it with a close investment. These cells divide once or twice at the top, so that 5 or 10 small cells are cut off, which project above the oogonium and form the so-called “crown” (Fig. 63 _k_). The crown either drops off at fertilisation, or its cells separate to form a central canal for the passage of the spermatozoids. The wall of the oosphere[9] above the receptive spot becomes mucilaginous, and allows the spermatozoid to fuse with the oosphere. The oospore, on germination (Fig. 64 _sp_), becomes a small filamentous plant of limited growth (Fig. 64 _i_, _d_, _q_, _pl_)--the proembryo--and from this, as a lateral outgrowth, the sexual generation is produced. The order is divided into two sub-orders:-- A. NITELLEÆ. The crown consists of 10 cells; cortex absent: _Nitella_, _Tolypella_. B. CHAREÆ. The crown consists of 5 cells; cortex present: _Tolypellopsis_, _Lamprothamnus_, _Lychnothamnus_, _Chara_. _Chara crinita_ is parthenogenetic; in large districts of Europe only female plants are found, yet oospheres are formed capable of germination.