110 



FOUNDATIONS OF BIOLOGY 



and associated tissues of the base of the pistil undergo more 

 or less profound changes ('ripen') and become transformed 

 into a FRUIT. The young sporophyte within, together with 

 food material for its further development, is hermetically 

 sealed up in a special packet it has become a SEED. 



FIG. 61. The life history of a higher Flowering Plant, from various species, a, 

 shoot of a Flax with flowers, X J; b, vertical section of a flower, XI; c, an anther 

 cut to show four microsporangia containing pollen grains (microspores), X6; d, an 

 ungerminated pollen grain, and one, e, which has formed tube (male gametophy te) , 

 X 110; /, longitudinal sections of an ovule enclosing megaspore and its contents 

 (female gametophyte) , X 20; g, an ovule transformed into a seed with young embryo 

 sporophyte and endosperm, X 10; h, a mature seed, X 5; i, youjig sporophyte from 

 the germination of the seed, X 5. (After Ganong.) 



In this form the new generation is prepared not only to 

 leave the parent plant and withstand adverse conditions for 

 a long time, but also to continue rapidly its development into 

 an adult sporophyte when it falls upon favorable soil. Inci- 

 dentally, it may be mentioned that the establishment of seed 

 formation is probably chiefly responsible for the dominant 

 position which the Flowering Plants hold in the flora of to-day. 

 (Fig. 61.) 



