78 



PRACTICAL BOTANY. 



and interest. Among the common organisms are the 

 following : 



Pandorina is a sphere made up of sixteen minute cells 

 inclosed in a gelatinelike mass. Each cell is provided 

 with a pair of flagella, which project through the gelati- 

 nous envelope. 



The reproduction of the plant is effected in two ways, 

 asexually and sexually. The asexual reproduction is by 

 the breaking up of each of the sixteen original cells into 

 , sixteen still more minute 



cells. The gelatinous 

 covering then dissolves 

 and sets these sixteen 

 young groups of cells 

 free. Each group be- 

 comes invested with an 

 envelope of its own and 

 develops into a full-sized 

 sphere. 



FIG. 36. - Pandorina morum Ehrb. a, Tne beginning of the 



swarming coenobium inclosed in a gel- sexual prOCCSS is similar 



atinous sheath ; b, c, swarm cells ; d, e, j. J.-L 1 TT Vi -F 



conjugation of gametes;/, resting spore. *P kne asexual. Jiacn OI 



(X 500.) (From Bennett and Murray, the Original sixteen cells 



after Pringsheim.) , , . , . . 



breaks up into sixteen 



cells, each of which is set free by the breaking away of 

 the gelatinous covering. Each cell is provided with two 

 flagella which enable it to move about. Two of these 

 cells meeting (Fig. 36, d and e) unite their contents into 

 a spherical mass which becomes invested with a cell wall. 

 The sphere thus formed is the resting spore. (Fig. 36,/.) 

 After a time, when the conditions for growth are favor- 

 able, the cell wall decays and sets free the two or three 

 little cells that have formed within it. Each of these 

 cells has a pair of flagella. After a period of activity, 

 it comes to rest, and the cell contents divide and sub- 



