Affinity of Gymnosperms with Angiosperms

 Affinity of Gymnosperms with Angiosperms : 

The gymnosperms resemble the angiosperms by the following features :

( 1 ) Both the groups , include trees and shrubs and may be erect , scandent or climbing .

( 2 ) The root system is well developed and the roots may be diarch , triarch , tetrarch or polyarch . The roots possess secondary growth . The xylem is exarch in the roots .

( 3 ) The stele of the stem is eustelic . The secondary growth is present in the stem . The secondary wood may be monoxylic or polyxylic.

( 4 ) Both the groups , produce seeds.

( 5 ) Both the groups are heterosporous and posses endosporic and reduced gametophytes .

( 6 ) The megaspore is in organic connection with the megasporangium and is never shed .

( 7 ) The nucellus is surrounded by an integument to form an ovule. The ovule has a micropyle and may be stalked or sessile.

( 8 ) The pollen grains grow into pollen tubes . 

( 9 ) The male gametes are non - motile in majority of gymnosperms and all angiosperms .

( 10 ) The male gametophytes are highly reduced . Gnetum lacks prothallus cells .

( 11 ) The germination of the spores is precocious . 

( 12 ) The embryogeny is endoscopic .