SEED-BEARING PLANTS 43 1 



OUTLINE OF LIFE HISTORY OF PINUS J 



The pine tree „ 



(Sporophyte) 



TT TT 



Carpellate cone Staminate cone 



(Modified branch) (Modified branch) — 



Ovuliferous scale Stamens 



(Homology obscure) (Microsporophylls) 



4,4. ii 



Ovule Anthers 



(Megasporangium) (Microsporangia) 



Megaspore-mother-cell Microspore-mother-cell 



4, < Reduction > J, 



Megaspore Jlicrospore 



I i 



Embryo-sac PoUen-grain 



(Female gametophyte) (Male gametophyte) 



i I 



Archegonium (Antheridial cell) 



Egg Sperm . 



Oosperm , 



ii 



Embryo (In a seed) 

 (Zygote) 



Embryo-rests 



Germination of seed 



Mature sporophyte (The pine tree) 



385. Comparison with Lower Forms. — It will be spe- 

 cially instructive, at this point, for the student to make a 

 careful comparison of the life history of Pinus with the 

 lower forms, such as Cycas, Selaginella, Lycopodium, Equi- 

 setum, and a true fern, noting especially the relative impor- 



