280 The Living Plant 



Asexual reproduction in the lower and simpler plants takes 

 place in two principal ways. In the tiniest plants, which com- 

 prise the Bacteria, or Germs, and some of the simplest Seaweeds, 

 the entire plant body consists of no more than 

 a single cell, which in reproduction splits di- 

 rectly across the middle; the two parts then 

 grow promptly to full size, only to split again, 

 and so on without limit (figure 93), a method 

 called fission, or division. Nothing could be 

 simpler, which explains the extreme rapidity of 



FIG. 93. Stages in the 



division of a one- multiplication in the forms that possess it. And 



C ^ s highly Sagm"- Jt is interesting to observe that this is exactly 



ftu'aplrt ecel (copied the method whereby single cells reproduce in 



from the Chicago even the highest of plants. A second method 



Textbook). 



of asexual reproduction in the simpler plants 

 consists in the formation of asexual spores, which, under great 

 diversity of habit and form, exhibit these features in common, 

 that they are single cells separated off from the parent plant, 

 and capable of growth directly each to a new plant. In some 

 Seaweeds they are provided with swimming appliances whereby 

 they can move through the water in a manner so suggestive of 

 animals that they are known scientifically as zoospores (figure 

 94), though in other Seaweeds 

 they are drifted passively about 

 by the water-currents. Non- 

 motile spores occur in many 

 land plants; are formed in pro- 

 fusion in the gills Of Mushrooms, FIG. 94. Forms of free-swimming repro- 

 thp ransillps of Mos^PS thp ductive cells, of which the two on the left 

 >es > T are asexual zoospores, while the two on 



brown SpOtS (or SOri), On the the^right are sexual cells, later to be de- 



under sides of the fronds of 



Ferns, and in the black stalked heads that develop on various 

 Molds (figure 95), whence they are wafted on the wings of the 

 wind to the uttermost parts of the earth. Oft-times these asexual 



