SEED-BKARING PLANTS 



OUTLINE OF LIFE HISTORY OF PINUS 



Tile pine tree 

 (Sporophyte) 



431 



Carpellate cone 

 (Modified branch) 



ii 



Ovuliferous scale 

 (Homology obscure) 



4.4. 



Ovule 

 (Megasporangium) 



ii 



Megaspore-mother-cell 



•4' ^ Reduction 



Megaspore 



I 



Embryo-sac 

 (Female gametophyte) 



i 



Archegonium 

 Egg 



TT 



Staminate cone 

 (Modified branch) 



4-4- 



Stamens 

 (Microsporophylls) 



4' 4' 



Anthers 

 (Microsporangia) 



Microspore-mother-cell 



^ 4. 



Microspore 



4. 



Pollen-grain 

 (Male gametophyte) 



4' 



(Antheridial cell) 



Sperm 



Oosperm 



4.4. 



Embryo (In a seed^ 

 (Zygote) 



4.4. 



Embryo-rests 



4-i 



Germination of seed 



4-4- 



Mature sporophyte (The i)ine 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 Finns with the 

 lower forms, such as Cycas, Selaginella, Lycopodium, EquU 

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



