Classification of Erythro Trichiaceae | Algae

In this article we will discuss about the classification of erythro trichiaceae.

Family Erythro Trichiaceae:

Algae belonging to this family possess filamentous branched, un-branched to thalloid plant body. Reproduction is by the development of large and small spores produced by the division of vegetative cells of the plant body.

Genus Compsopogon of Erythro Trichiaceae:

Compsopogon is chiefly confined in the tropical and subtropical fresh water streams. It occasionally occurs in bunches along the edge of the ponds being attached to submerged aquatic plants, other plant parts (Fig. 130A & B), bricks, etc., also in mud below water-level. The alga when growing in still water may remain unattached. In West Bengal, it appears in January and disappears with the advent of hot season.

Plant body is filamentous and always more or less copiously branched (Fig. 130C). In the coarse mature regions, the filament is blue-green in colour. The younger parts of the filament are uniseriate with discoid cells (Fig. 130A & D) and the mature parts are with an axial row of cells which become greatly enlarged being barrel-shaped and are surrounded by one or more layers of cortical cells (Fig. 130B).

The outermost cortical cells are smaller with inner cortical cells being progressively larger (Fig. 130F). The axial cells in very old filaments breakdown and are replaced by the enlarged cells of the inner cortex.

The filaments increase in length through intercalary divisions, and at no great distance from the terminal cell longitudinal septa begin to make their appearance, irregularly at first, but succeeding one another in such a fashion that central axial cell is separated from a layer of deeply pigmented small peripheral cells (Fig. 130E) that completely surround it and continue to undergo anticlinal divisions without regularity, while the axial cell constantly enlarges assuming a flattened barrel-shaped form (Fig. 131M).

These pigmented cells constitute the cortex around the large almost colour­less cell which is filled with watery contents and contains few chloroplasts. The ori­ginally single cells of the younger filaments are thus converted into corticated seg­ments indicated by slight constrictions in the older filaments.

The monstrously deve­loped axial cells form a continuous axial series (Fig. 130F). This cortical layer is lacking in the basal part of the thallus.

Here the cells are commonly overgrown by septate rhizoids which perform the function of anchorage. Young individual after attaining a certain length begins to give rise to a sub-dichotomous branch, and the main axial portion becomes somewhat arched.

Subsequently a second sub-dichotomous branch arises on the same side of the axial portion from a cell nearer to the apex. This branch behaves in a similar manner and a further arching of the main axis towards the substrate takes place. With repeated branching several branches and branchlets are formed resulting in the formation of a richly branched bluish-green or violet- green coloured macroscopic thallus.

The primary filament and the branchlets are distinctly constricted at the joints. Cells of the thallus are uninucleate containing nume­rous spherical chromatophores which are densely aggregated to the cell wall. There are no pit-connections between the adjacent cells.

The method of reproduction so far reported is asexual by monospores. The monospores are non-flagellate spherical spores with a large nucleus embedded in dense cytoplasm. They are of two kinds being borne in sori of microsporangia (Fig. 130 H & I) and some are developed in solitary macrosporangia (Fig. 130 K & L).

Both kinds of sporangia are developed either from the cortical cells or from cells cut off from the un-corticated cells (Fig. 130 G & J).

The microsporangia sori are more or less hemispherical to oblong in shape and consist of 15-25 or even more microsporangia. The microsporangia are normally spherical, but very commonly polyhedral due to mutual pressure. They may arise from any cell of the filament appearing as scattered minute heaps of cells (Fig. 130 H & I).

During the formation of spores the contents of each microsporangium con­tract and become spherical. The spores are borne singly in each microsporangium. The micro-sporangial wall opens by a slit and the spore is discharged with a jerk. The spore thus liberated secretes a wall and directly develops into a new plant.

The macrosporangia are developed in rather restricted areas of the filament. The formation of each macrosporangium is initiated by the appearance of a septum in the cell from the daughter cell of which the macrosporangium will be ultimately pro­duced. The septum separates the cell into two daughter cells.

The daughter cell which ultimately matures into a macrosporangium has denser contents and the nucleus larger and more conspicuous (Fig. 131A) than the other daughter cell.

The separation of daughter cells takes place during night. As the day advances the protoplast of the cell and its wall assume a sub-triangular outline (Fig. 131B). One of its rounded angles projects in the form of a papilla. The cell then becomes a macrosporangium (Fig. 131G).

The basal septum of the macrosporangium which originally separated it from the other daughter cell bulges more and more strongly towards the macrosporangium, and finally the discharge of the spore is accomplished by the dehiscence of the papilla, slowly at first and then more rapidly (Fig. 131D & E).

The basal septum then reverses to its previous position. The position of the sporangium is merely indicated by the slightly projecting margins of the orifice through which the spore escaped (Fig. 130L). The spore which is discharged with a force is sufficient to carry to a very short distance from the filament.

Each macrosporangium produces a single spore which is spherical, completely filled with chloroplast, except for a small area (Fig. 131E). The liberated spore directly germinates into a new filament.

The spore on coming into contact with the substratum becomes somewhat flat­tened at the surface of contact and then divides to form a short-creeping filament of three or four cells (Fig. 131 I to H). Then one to two of these cells give rise to a short lateral branch (Fig. 131 I to K). Subsequently, a cell in a median position elongates vertically and forms the initial cell of an erect filament (Fig. 131L).

It divides to form a dome-shaped apical cell which gives rise to discoid segments. In the latter stages, the growth is by the division, largely, of these segments with the gradual differentiation of central axial cells and peripheral cells (Fig. 131M).

The initiation of the erect portion of the filament curtails further extension of the creeping portion which, therefore, remains small. In fact, the attachment of the thallus is subsequently augmented by a rhizoidal development. The erect filament is at first uniseriate, but in the later stages the cells, a little distance from the apex, enlarge and divide, forming a peripheral layer of small cortical cells.

This involves a lateral expansion of the thallus. The distal part of the filament remains uniseriate and the cells of this region contribute to the growth in length of the filament.

As any or all of the cells in this region are capable of division in a transverse plane, it constitutes a growing region. The lowermost few cells of the erect filament do not form a cortical layer but only bear rhizoids as tubular extensions at the lower ends. These rhizoid- bearing cells are delimited early in the development of the erect portion before the formation of the corticated portion of the filament.

Thus, the filament consists of three regions:

(i) The growing region,

(ii) The region differentiated into cortical and axial cells, and

(iii) The rhizoidal region. A striking analogous condition to higher plants thus exists so far as the general developmental pattern of the alga is concerned.

Some Indian Species of Genus Compsopogon:

Compsopogon coerulens (Balbis) Mont.; C. hookeri Mont.; C. indica Das; C. iyengarii Krishnamurthy; C. lividus (Hooker) Detoni.

Special Features of Genus Compsopogon:

1. Copiously branched filamentous macroscopic thallus.

2. Thallus differentiated into growing region, region differentiated into cortical and axial cells, and the rhizoidal region.

3. Asexual-reproduction by non-flagellate spores—the monospores.

4. Monospores borne singly in microsporangia and macrosporangia.

5. Microsporangia are developed in sori, whereas, the macrosporangia are solitary.