THE PLANT OVUM 69 



complex they may be in their adult condition, originate as 

 unicellular bodies of microscopic size. 



The same is the case with all the higher plants. The 

 pistil or seed-vessel of an ordinary flower contains one or 

 more little ovoidal bodies, the so-called " ovules " (more 

 accurately megasparangia (see Lesson XXX., and Fig. 89), 

 which, when the flower withers, develop into the seeds. A 

 section of an ovule shows it to contain a large cavity, the 

 embryo-sac or megaspore (see Fig. 89, F), at one end of 

 which is a microscopic cell (Fig. 12, B), consisting as usual 

 of protoplasm (plsni), nucleus (?/), and nucleolus (;///). 

 This is the ovum or egg-cell of the plant : from it the new 

 plant, which springs from the germinating seed, arises. Thus 

 the higher plants, like the higher animals, are, in their 

 earliest stage of existence, microscopic and unicellular. 



