234 



PLANT LIFE. 



always occurs when they are unequal. A corresponding dif- 

 ference in size is often found between the sporangia con- 

 taining small spores (microsporatigia) and those containing 

 large spores (megasporangia) (figs. 241, 242 1. 



The sex terms, male and female, applicable primarily to 

 the sex cells, arc applied also to the organs and to the plants 



240. 



Fig. 240. — Sporophyte of a club-moss (Lycopodium clavatnm). The horizontal stem 

 is densely covered with leaves ; those OB the erect branch become small and few tor a 

 space: these are succeeded by broader leaves, the sporophylls, crowded in a dense 

 spike, s. Half natural size.— After I'rantl. 



Fig. 241. — Section through three sori of an aquatic femwort {Salvinia natans). 

 Each is covered by a double indusium. r, /. two sori consisting of sporangia con- 

 taining microspores <see tig. 242); <». a sorus consisting of sporangia, each containing 

 one megaspore. M agnified 10 diain. After Sachs. 



which bear them, so that the microspores are said to produce 

 male plants, and the megaspores female plants. For a fur- 

 ther account of the gametophyte, see • 386, 394, 393. 



328. Seed plants. — In the seed plants this differentiation 

 of the spores is always found. The microspores are called 



