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tive structure of the plant, the short and broad cells of the main 
branches and the much smaller ones of the branchlets. 
5. A GREEN SEAWEED (Anadyomene stellata). 
A representative of a family of seaweeds which is chiefly con- 
fined to the warmer parts of the earth. In some of the smaller 
compartments are formed a great number of microscopic motile 
spores or propagating cells, which finally escape through an open- 
ing in the wall. After swimming about for a time, these motile 
spores come to rest and develop new plants. 
6. A Brown SEeaweeD (Ectocarpus stliculosus). 
The plant consists of delicate branching threads, each part in 
the ordinary vegetative condition being made up of a single row 
of cells. The structures resembling an ear of corn produce 
minute motile reproductive cells, which unite in pairs before giv- 
ing rise to new plants. The species of Actocarpus often grow 
attached to the larger seaweeds. 
7. A Rep Fresu-waTer Aca (Satrachospermum). 
One of the larger forms of the algae inhabiting fresh water. 
The main branches are peculiarly constructed; at first they 
consist of a single series of large cells, this structure becoming 
subsequently surrounded by numerous smaller cells, and its ap- 
pearance being in consequence much changed. The gelatinous 
masses formed by this plant are slightly suggestive of frog- 
spawn, whence the Latin name, Batrachospermum. 
8. A RED SEAwzED or “Sea-Moss” (Prilota elegans). 
This species is found on the under side of shelving rocks 
between the tide-marks and is sometimes waehed ashore from 
eep water. The color, now faded, is, when living, dark red 
or nearly black. This plant exemplifies well the pinnate type of 
branching. 
9. A SEAWEED oR “Sea-Moss” (Polysiphonia). 
The branching filaments which make up the plant body are 
here regularly jointed. Each joint consists of a bundle of more 
or less elongated cells surrounding in a single layer, in this 
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