Which group of plants lacks differentiated organs such as roots,stems,and leaves?

The filaments of $Spirogyra$ are:

Read carefully the given statements about algae and choose the correct option.
$I$. The plant body is thalloid.
$II$. Mainly aquatic.
$III$. Reproduction takes place by vegetative,asexual,and sexual methods.
$IV$. Volvox and Ulothrix are the colonial forms of algae.

In which plant group are the reproductive organs not surrounded by a layer of sterile cells?

The filament of $Mastigocladus$ $laminosus$ is

Red algae generally do not produce $......$.