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.
[Illustration: FIG. 64.--_Chara fragilis._ Germinating oospore
(_sp_); _i_, _d_, _g_, _pl_, form together the proembryo rhizoids
(_w′_) are formed at _d_; _w′_ the so-called tap-root; at _g_ are
the first leaves of the sexual plant, which appears as a lateral
bud.]
About 40 species of fossilized _Chara_, determined by their carpogonia,
are known in the geological formations from the Trias up to the present
day.