The figures included in the text are intended to illustrate in very simplified and indicative form the basic physical characteristics of some of the world's major seaweeds. For each alga the taxonomic name is given together, where appropriate, with the common or “popular” name. Whether the species is classified as brown, red or green is noted by the abbreviations (Br), (R) or (Gr) respectively.
The figures are to be found in the text as follows:
A broad indication of the average size (height) is given by the use of the following groups:
| Very large | (V.Lg.) | i.e., greater than 10 m |
| Large | (Lg.) | i.e., between 1 and 10 m |
| Medium | (Med.) | i.e., between 0.3 and 1 m |
| Small | (Sm.) | i.e., between 0.05 and 0.3 m |
