CHAPTER XIV. 



ALG.E. 



THE Algce form an important order of cryptogamic 

 plants, comprising, however, the very simplest of all 

 plants. It includes at once some of the smallest and 

 some of the largest of plants, among the former being 

 many of the interesting microscopic organisms re- 

 ferred to briefly in Chapter I. Most of them are 

 marine or freshwater plants, only a few species being 

 found on land. All the seaweeds of our coasts, with 

 their lovely tints and beautiful forms, are Alg<%. They 

 are characterised by the entire absence of true roots. 

 Many of them are attached to the rocks by pseudo- 

 roots; but attachment seems to be the only advan- 

 tage obtained by this arrangement. Instead of being 

 dependent upon these pseudo-roots for nourishment, 

 they absorb it through every part of their surface. 

 They are entirely cellular in their structure, though 

 a few possess organs closely approaching to vessels. 

 In outward form they exhibit a remarkable amount 

 of variation, many of the higher forms being pos- 

 sessed of thick, solid stems, like tree-trunks, as in 

 Lessonia, which forms submarine forests. In the 

 opposite direction, we have such forms as Protococcus^ 

 Desmid, and Volvox, which consist of a single cell 



