324 



GENERAL BOTANY 



microspores bore into this sporangial tissue and absorb nourish- 

 ment for the developing gametes. When the eggs are ripe, the 

 sporangial tissue between the pollen chamber and the female 



gametophyte breaks down and the 

 motile male gametes are cast out into 

 a depression in the gametophyte, called 

 the archegonial chamber, into which 

 the necks of the archegonia open. Fer- 

 tilization takes place when a motile 

 male gamete bores through the neck of 

 the archegonium and fertilizes the egg. 

 Embryo and seed. The embryo spo- 

 rophyte bores its way into the gameto- 

 phyte tissue, much as in Selaginella, by 

 means of a suspensor. The mature 

 embryo in the seed consists of two cotyledons, a hypocotyl, 

 and a plumule (Fig. 188). The seed is therefore much like 

 that of the higher plants studied in Part I and consists of the 

 seed coat, or integument, a mere remnant of the megasporan- 

 gium, the gametophyte, and the embryo sporophyte. Zamia 



Micrvpyle 



FIG. 188. Seed of Zamia with 

 embryo 



Sporophyte plant 



Gametophyte organs Gametes 



Gametophyte Sporophyte 



FIG. 189. Life history of Zamia represented graphically 



is thus the first plant among the plant groups now under con- 

 sideration which forms a true seed. Germination of the seed 

 results in a seedling sporophyte which develops into the mature 

 Zamia plant, similar in habit to Diom (Fig. 186). 



