In our chapter on plant life we mentioned that many coloured plants contained the green colouring matter, chlorophyll, just as do the ordinary green leaves. We showed too that by boiling some green leaves in methylated spirits we could extract the chlorophyll and that its solution had the peculiar property of appearing green when light passes through it and red when light is reflected from it. If now we take almost any brown or red seaweed, we cannot see a trace of chlorophyll anywhere. Let us leave our specimen, however, in fresh water for a few days when we shall find that the brown or red colouring matter as the case may be, is dissolved by the water and a green plant remains. By treating the seaweed, deprived of its distinctive colour, with methylated spirit as described above, we can obtain a solution of chlorophyll. The microscopist who is anxious to make a study of seaweeds, will find little scope for his hobby on a sandy shore. Just as the most interesting marine animals are to be found where rocks abound, so must we hunt in similar situations for our _Algæ_. A few thread like _Algæ_ are able to anchor themselves to the sand but most of them require a substantial support. A bare rock is a much favoured situation and before we have learned the peculiarities of these plants we may marvel how they obtain any sustenance from so barren a resting place. As a matter of fact they derive no nourishment from the rocks on which they rest. The part of the sea weed which, in our ignorance, we may have dubbed a root, is nothing of the kind. It bears no relationship to the roots of higher plants and is a mere anchor, designed to fasten its owner to a support. None of these plants have roots, none have true stems or leaves, though the parts resembling stems and leaves are often so called; none of them flower and so fruits and seeds are unknown to them. Their food is absorbed from the sea water over the whole of their surface.