150 ELEMENTARY STUDIES IN BOTANY 



sperms), and then penetrate the tip of the ovule until the egg 

 is reached. 



The second feature is the appearance of the flower, which 

 differs from a strobilus in having another set of members 

 added to the sporophylls, and this set (perianth) is generally 

 differentiated into sepals (calyx) and petals (corolla). 



The third feature is related closely to the second, for it is 

 the development of insect-pollination. Many Angiosperms 

 retain the old method of wind-pollination, but insect-pol- 

 lination is a conspicuous feature of the group, and it is as- 

 sociated with the remarkably diversified development of 

 flowers. 



In addition to these conspicuous features of Angiosperms, 

 there are two others that should be remembered. The 

 gametophytes are reduced to their lowest terms, and two 

 kinds of embryo are formed (dicotyledonous and monocotylc- 

 donous) . 



