Division III. STEPHA1S OKONT^E 



The group-name ' Stephanokontse ' was suggested by Blackman & Tansley 

 ('02) for those Algje in which the motile reproductive cells possess a crown 

 of cilia round the clear anterior end. As a divisional name it stands on an 

 equal footing with the Isokontre, Akontse and Heterokonta3. The Algee 

 included in it are filamentous, with a great uniformity of morphological 

 characters, and they constitute one of the most distinctive orders of the 

 Chlorophycese, not only because of the peculiar nature of their ciliated 

 reproductive cells, but also on account of the unique type of division of their 

 vegetative cells. 



Order 1. CEDOGONIALES. 



In this order the thallus consists of fixed, simple or branched filaments, 

 with a wide range of thickness in the various species. There are only three 

 genera. (Edogonium, Bulbochtete and (Edocladium, the first-named having 

 simple filaments and the two others branched filaments. The following 

 account of the structure and reproduction refers to the genera (Edogonium 

 and Bulbochsste, the third genus (Edocladium being dealt with separately. 



In the young stages of these plants there are well-marked organs of 

 attachment, although many species of (Edogonium float freely when adult. 

 The distinction between base and apex is, however, never lost and can be 

 discerned in every individual cell in the filament. In almost all cases the 

 apical part of the cell is somewhat wider than the basal part and very often 

 slightly tumid. (Consult fig. 240 A C; fig. 246 B; etc.) There is also 

 a characteristic rigidity about a filament of (Edogonium which precludes any 

 such graceful bending as may be noticed in the flexible filaments of Spirogyra 

 or Ulothrix, and in many of the smaller species there is an inequality in the 

 growth of the individual cells which gives rise to irregular twists and turns 

 in the filament 1 . The basal cell invariably differs from the other cells ; it is 



1 This feature reminds one of the similar unequal growth of the segments of a Rlnzoclonium- 

 filarnent (vide p. 267). 



w. A. 25 



