Affinity of Gymnosperms with Pteridophytes

Affinity of Gymnosperms with Pteridophytes : 

The gymnosperms resemble the pteridophytes by the following features :

(1) Both possess independent sporophytes which are differentiated into root , stem and leaves . Both the groups exhibit heterosporous life cycle .

(2) The sporophytes possess a well developed vascular system such as xylem and phloem . The xylem in most of the members of groups lacks vessels and the phloem lacks companion cells .

(3) Many Cycads resemble the ferns in possesing large compound leaves and the in the circinate ptyxis of the leaves . Dichotomous venation in Ginkgo and ferns .

(4) The female sex organs are archegonia in both the groups .

(5) The male gametes of Cycads and Ginko are motile , like the pteridophytes . 

(6) Many pteridophytes like Marselia,Salvinia , Azolla, Isoetes and Selaginella are heterosporous like the gymnosperms .

( 7 ) Some of the heterosporous pteridophytes possess one megaspore in the megasporangium , like the gymnosperms .

( 8 ) The gametophytes of gymnosperms and heterosporous pteridophytes are endosporic .

(9) In both , the gametophytes are highly reduced and they are developed within the spore wall in some pteridophytes . The male gametophytes of heterosporous pteridophytes and majority of gymnosperms possess only two male prothallial cells .

(10) The female prothallus develops before fertilization and there is free nuclear division .

( 11 ) Development of a distinct embryo after fertilization . The embryogeny is endoscopic in many pteridophytes and all gymnosperms .

( 12 ) Germination of spores is precocious in gymnosperms and heterosporous pteridophytes . 

( 13 ) In the life-history, both sporophytic and gametophytic generations alternate regularly with each other .