126 



Aquatic Organisms 



posed in anastomosing bands. The thick cell walls, 

 some of which show a peculiar cross striation near one 

 end of the cell, are ready means of recognition of the 

 members of this great genus. The filaments are 

 attached when young, but break away and float freely 

 in masses in quiet waters when older; it is thus they 

 are usually seen. Conferva (Tribonema) abounds in 

 shallow pools, especially in spring time. Its filaments 

 are composed of elongate cells containing a number of 



separate disc-like chlor- 

 ophyl bodies. The cell 

 wall is thicker toward 

 the ends of the cell, and 

 the filaments tend to 

 break across the middle, 

 forming pieces (halves of 

 two adjacent cells) which 

 appear distinctly H- 

 shaped in optic section. 

 This is a useful mark 

 for their recognition. It 

 will be observed that 

 these then are similar 

 in form and habits to 

 the filamentous conju- 

 gates discussed above, 

 but they have not the 

 peculiar form of chlor- 

 ophyl bodies characteristic of that group. (Eodgonium 

 is remarkable for its mode of reproduction. 



2. Branching filamentous forms — Of such sort are a 

 number of tufted sessile algae of great importance: 

 Cladophora, which luxuriates in the dashing waterfall, 

 which clothes every wave-swept boulder and pier with 

 delicate fringes of green, which lays prostrate its pliant 

 sprays (fig. 46) before each on-rushing wave, and lifts 



Fig. 47. Two species of Chactophora, 

 represented by several small hemi- 

 spherical colonies of C. pisiformis and 

 one large branching colony of 

 C. incrassata. 



