Chara crinita is parthenogenetic; in large districts of Europe only female plants are found, yet oospheres are formed capable of germination.
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.
Class 8. Phæophyceæ (Olive-Brown Seaweeds).
The Phæophyceæ are Algæ, with chromatophores in which the chlorophyll is masked by a brown colour (phycophæin). The product of assimilation is a carbohydrate (fucosan), never true starch. In the highest forms (Fucaceæ), the thallus presents differentiation into stem, leaf, and root-like structures. The asexual reproduction takes place by means of zoospores. The sexual reproduction is effected by the coalescence of motile gametes, or by oogamous fertilisation. The swarm-cells are monosymmetric, each moved by two cilia which are true protoplasmic structures, and generally attached laterally (Fig. [65]). The Phæophyceæ are almost entirely saltwater forms; a few species of Lithoderma live in fresh water.
The class is divided into two families:—
1. Phæosporeæ: 1 Sub-Family, Zoogonicæ; 2 Sub-Family, Acinetæ.
2. Cyclosporeæ: Fucaceæ.