the brown colouring matter which is added to chlorophyll is identical with phycophaein; two varieties of it have been termed phycopyrrin and peridinine. Certain species, such as Gymnodinium spirale, are colourless and therefore saprophytic in their method of nutrition. Multiplication takes place in some cases by the endogenous formation of zoospores, the organism having come to rest; in others by longitudinal division, when the organism is still motile. No method of sexual reproduction is known with certainty.
| A. | Halopteris, apical region. |
| B. | Chordaria sp., apical region showing so-called trichothallic growth. |
| C. | Dictyota sp., apical cells immediately after dichotomy. |
| D. | Cutleria sp., margin of thallus showing trichothallic growth. |
| E. | Halidrys, apical depression with leading cell. |
| F. | Macrocystis sp., tubular elements from the medulla, with sieve-like transverse walls. |
| G. | Laminaria sp., hyphae with trumpet-like ends also from medulla. |
| H. | Elachistea sp., plurilocular sporanges. |
| K. | Ectocarpus sp., unilocular sporange. |
| L. | Ectocarpus siliculosus, female gamete surrounded by male gametes. a, b, c, d, e, stages of conjugation. |
| M. | Cutleria multifida. a, antherozoids, b, a female gamete. |
| N1. | Fucus vesiculosus, young oogonium. |
| N2. | Fucus vesiculosus, discharge of eight oospheres from oogonium. |
| O. | Laminaria sp., sporanges among paraphyses. |
| P. | Dictyota dichotoma, a sorus of oogonia. |
| Q. | Dictyota dichotoma, part of a sorus of antheridia. |
(A, B, C, D, E, H, L, M, P, from Engler and Prantl, by permission of Wilhelm Engelmann; F, G, K, O, from Oltmanns, by permission of Gustav Fischer;
Q, from The Annals of Botany, by permission of the Clarendon Press; N1, N2, from Hauck, Meeresalgen, by permission of Eduard Kummer.)
The Cryptomonadaceae also are unicellular, and live free or in colonies. Each cell contains a flattened chromatophore of a brown or yellow colour. Hydrurus forms a branched gelatinous colony attached to stones in mountain streams. Chromophyton forms an eight-celled colony. Both plants multiply solely by means of zoospores. The Cryptomonadeae and Chromulineae are motile through the greater part of their life. Cryptomonas, when dividing in a mucilage after encystment, recalls the condition in Gloeocystis. In Synura and Chromulina the cells form a spherical motile colony, recalling Volvocaceae. Chromulina is uniciliate, and is contained in a hyaline capsule. Like the Peridiniaceae, the Cryptomonadaceae have been included among Flagellata. They have no close affinity with Euphaeophyceae. Such colonial forms as Hydrurus and Phaeocystis are supposed, however, to indicate a stage in the passage to the multicellular condition.
Diatomaceae have long been recognized as plants. Together with Peridiniaceae they constitute the bulk of marine plankton, and thus play an important part in the support of marine animal life. They exhibit striking adaptations in these circumstances to the floating habit. (See Diatomaceae.)
A census of Phaeophyceae is given below:—
- Cyclosporinae (Fucaceae)—4 families, 32 genera, 347 species.
- Tetrasporinae (Dictyotaceae)—1 family, 17 genera, 130 species.
- Phaeozoosporineae (Phaeosporeae)—24 families, 143 genera, 571 species.
(De Toni’s Sylloge Algarum.) - Peridiniales—3 families, 32 genera, 167 species.
- Cyrptomonadaceae (including Chrysomonadaceae)—2 families, 28 genera, 50-60 species.
- Bacillariales (Diatomaceae)—about 150 genera and 5000 species, fossil and recent.
(Engler and Prantl’s Pflanzenfamilien.)
IV. Rhodophyceae, or Florideae.—The members of this group are characterized by the possession of a red colouring matter, phycoerythrin, in addition to chlorophyll. There is, however, a considerable amount of difference in the shades of red which mark different species. The brightest belongs to those species which grow near low-water mark, or under the shade of larger algae at higher levels; species which grow near high-water mark are usually of so dark a hue that they are easily mistaken for brown seaweeds. Rhodophyceae are mostly marine, but not exclusively so. Thorea, Lemanea, Tuomeya, Stenocladia, Batrachospermum, Balbiania are genera belonging entirely to fresh water; and Bangia, Chantransia, Caloglossa, Bostrychia and Delesseria contain each one or more freshwater species. Most of the larger species of marine Rhodophyceae are attached by means of a disc to rocks, stones or shells. Many are epiphytic on other algae, more especially the larger Phaeophyceae and Rhodophyceae. As in the case of epiphytic brown seaweeds, the rhizoids of the epiphyte often penetrate the substance of the supporting alga. Some Red Algae find a home in the gelatinous substance of Flustra, Alcyonidium and other polyzoa, only emerging for the formation of the reproductive organs. Some are perforating algae and burrow into the substance of molluscan shells, in company with certain Green and Blue-green Algae. Some species belonging to the families Squamariaceae and Corallinaceae grow attached through their whole length and breadth, and are often encrusted with lime. The forms which grow away from the substratum vary greatly in external configuration. In point of size the largest cannot rival the larger Brown Algae, while the majority require the aid of the microscope for their investigation.
No unicellular Rhodophyceae are known, although a flagellate organism, Rhodomonas, has recently been described as possessed
