224 



PART III. THE CLASSIFICATION OF PLANTS. 



The leaves vary in form. In some cases (e.g. Caulerpa, Fig. 

 162 ; Sargassum) they resemble the foliage-leaves of the higher 



B. 



FIG. 160. Growing-points of Algae. A apical growing-point, with apical cell, of 

 Stypocaulon scoparium (x30). B intercalary trichothallic growing-point (where the 

 transverse lines are close together) of Desmarestia ligulata in longitudinal section ( x 60). 

 C apical growing-point, with apical cell, of Chcetopteris plumosa (x 40) (after Falkenberg). 



plants ; in others, (e.g. Cladostephus, Chara) they resemble the 

 stem and its branches, but are distinguished by their limited 



growth : in others again (e.g. 

 Polysiphonia and other Rho- 

 dophyceae, Fig. 161), they 

 are filamentous and hair-like. 

 The morphology of the 

 reproductive organs is dis- 

 cussed in connexion with the 

 processes of reproduction. 



The Reproduction of the 

 Algae is effected in various 

 ways. Vegetative multipli- 

 cation takes place in the 

 unicellular forms (e.g. Cyano- 

 phycese, Protococcoideae, Des- 

 midieae, etc.) by cell-division, 

 in some of the higher forms 

 (e.g. Sphacelaria, Chara, 

 Melobesia) by means of mul- 

 ticellular gemmae (see p. 68). 

 Non-motile cells, with a cell- 

 wall, which are probably 



FIG. 161. Polysiphonia (Herposiphonia) (after 

 Naegeli). The dorsi ventral horizontal stem 

 bears the leaves (/) on the dorsal surface ; the 

 root-hairs (r) on the ventral surface; and the 

 branches (a b c) on the flanks. 



gemmae, 



are 

 are thrown off by 



