Bryopsidales is an order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of green algae

Green algae

The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...

, in the class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Bryopsidophyceae

Bryopsidophyceae

Bryopsidophyceae is a class of chlorphyte green alga.-Links to scientific databases:...

.

Characteristics

The thallus is filamentous and much branched and may be packed into a mass. It is coenocytic

Coenocyte

A coenocyte is a multinucleate cell. It can result from multiple nuclear divisions without accompanying cell divisions, or from cellular aggregation followed by dissolution of the cell membranes inside the mass. Coenocytes are found in fungi and some protists, such as algae and slime mold. Some...

, having multi-nucleate cells consisting of cytoplasm

Cytoplasm

The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

 contained within a cylindrical cell wall

Cell wall

The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

. There are no septae

Septum

In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...

 and the many discoid chloroplasts, nuclei and other organelle

Organelle

In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....

s are free to move through the organism. The whole organism may consist of a single cell and in the genus Caulerpa

Caulerpa

Caulerpa is a genus of seaweeds in the family Caulerpaceae . They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world...

this may be several metres across. In the genus Halimeda

Halimeda

Halimeda is a genus of green macroalgae. The algal body is composed of calcified green segments. Calcium carbonate is deposited in its tissues, making it inedible to most herbivores....

, whole seabed meadows may consist of an individual, single-celled organism connected by filamentous threads running through the substrate.

Reproduction

Propagation is normally vegetative

Asexual reproduction

Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...

 from small fragments which grow into new individuals. Under certain conditions sexual reproduction occurs in a process called holocarpy. Almost all of the cytoplasm in the thallus is converted into biflagellate gamete

Gamete

A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...

s, which are discharged into the sea through papillae. After fertilisation, the zygote

Zygote

A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

 becomes a protonema

Protonema

A protonema is a thread-like chain of cells that forms the earliest stage of a bryophyte life cycle...

and this in turn develops into a new thallus.