6 BOTANY AND PHARMACOGNOSY. 



In both lower and higher plants, with the exceptions just 

 noted, reproduction is also carried on by means of spores. 



Depending upon their origin two classes of spores are distin- 

 guished, namely, (a) asexual spores, and (b) sexual spores. In 

 the production of asexual spores the contents of a certain cell 



Fig. 5. Ulothrix zonata. A, young filament with rhizoid cell (r); B, piece of filament 

 showing escape of swarm spores; C, a swarm spore or zoospore with 4 cilia; D, biciliate 

 gametes escaping from a filament; E, F, G, showing different stages of union of two gametes; 

 H, young zygote or zygospore in which the cilia have been absorbed; J, i-celled plant 

 developed from zygote; K, young plant organizing zoospores. After Dodel-Port. 



called a mother cell or sporangium break up into a number of 

 new cells sometimes called daughter cells, which escape through 

 the cell wall. In the lower plants, particularly those growing 

 in water or in moist places, these cells are provided with short 



