116 



MOVEMENT 



movement of their own. Certain of them, however, propel 

 their bodies through the water by means of the lashing of a 

 long, whip-like flagellum. Very often there are two flagella, 

 and sometimes there are ciha. Then, again, the antherozoid 

 of plants — the male cell, corresponding with the animal 

 spermatozoon — which fertilizes the egg of the plant, is motile. 

 For instance, in a fern the antherozoid swims through 

 water to make its way to the egg or ovum, and this is true 



Fig. 36. Horizontal underground stem, or rhizome of a Sedge, sending roots 

 downwards and leaves upwards. From Le Maout and Decaisne. 



of many plants, even as high as the sacred Chinese maiden- 

 hair tree, Gi^igko. The bracken-fern, Pteris, does, how- 

 ever, move. Its creeping underground stem, or rhizome, is 

 always pushing forward in the soil. The front end grows and 

 the hind end decays. The leaves or fronds are borne near the 

 latter end, they die doAvn during the autumn, and the next 

 year's fronds will be borne an inch or two further along the 

 rachis, nearer to the front end, to the growing-point. Thus 

 the whole fern, slowl}^, very slowly, moves forward. Sedges 

 and some other plants also have underground stems which 



