240 
STRUCTURE AND LIFE HISTORIES 
as the gametes are set free fertilization takes place, pro- 
ducing a fertilized egg, with, of course, the double or diploid 
number of chromosomes. Every cell of the sporeling, 
resulting from the germination of the oosperm, and every 
cell of the mature plant into which it develops, possesses 
the double number, up to the first two divisions of the 
-........l"-V At) / 
''.. : >:'-:: T Gametopbyte / Sporophyte 
: ' /: ^ I Stage I Stage 
FIG. 176. Diagram of life-cycle of Ascophyllum nodosum. 
young gametangia, when reduction gives rise to gameto- 
phytic cells. The fusion of these egg with sperm in 
fertilization restores the double or sporophytic number 
and so on in cycle after cycle (Fig. 176). 
225. Diagram of Life History. The successive steps in 
the life cycle of Ascophyllum may be briefly summarized 
as follows: 
