212 



Cook : Potamogeton lucens 



Figs. a-/. Diagrammatic drawings showing the shape and relative sizes of the 

 embryo-sac, embryo, and ovule at various stages of their development. Also, the wal 

 across the sac in a, b, c, d ; the mass of small nuclear cells at the antipodal end of the 

 sac in b, c, d, e 9 f; the core of elongated cells in d and e ; and the third chamber to/ 



and the mass of small nucellar cells is quite prominent ; in c the 

 sac is still larger and the embryo is in the stage corresponding 

 figure 15 ; in d both the sac and the embryo are very much larg 

 the embryo at this time being" about the age indicated m figure i 



to 



