148 



STRUCTURAL BOTANY 



"o 



FIG. 66. General view of a very 

 small female plant of CEdogonium 

 ciliatum. b, the attaching disc ; 

 $, ?, two oogonia, the upper of 

 which has opened by a lid at the 

 top, and contains the fertilised 

 oospore ; the lower is still closed, 

 and the ovum unfertilised, cf, $, 

 dwarf males, adhering to the 

 oogonia. The uppermost has 

 opened to discharge a spermato- 

 zoid. Magnified 166. (After 

 Pringsheim. 1 



tank, though less common 

 in running water. The 

 (Edogonia are filamentous, 

 the individual threads 

 being only just distin- 

 guishable by the naked 

 eye, and grow attached to 

 stones, piles, larger water- 

 plants, or, in fact, to any 

 submerged object, forming 

 a dark-green downy coating 

 upon it. 



Fig. 6 6 shows the whole 

 of a small plant of CEdogon- 

 ium ciliatum, highly magni- 

 fied ; the specimen is much 

 below the usual size. The 

 main outlines of the struc- 

 ture, however, are always 

 the same, the whole plant 

 consisting of a single row of 

 cylindrical cells, attached 

 at one end, which we may 

 call the radical end. The 

 root - cell contains less- 

 chlorophyll than the others. 

 It is expanded into a flat- 

 tened disc, which forms a 

 holdfast, but probably does- 

 not take any special part- 

 in the absorption of food. 

 /"Fresh -water Algse absorb 

 their food, mineral as well 



