THE ENDOSPERM 



249 



are large and conspicuous, remain in their usual position in the basal 

 part of the embryo sac. Two endosperm chambers are formed 

 after the first division, but the chalazal is situated toward one side 

 rather than directly over the antipodal cells (Fig. 141C). For a 

 time free nuclear divisions take place in both chambers. Later 

 cell formation occurs in the mi- 

 cropylar chamber, while the cha- 

 lazal one degenerates. 



Svensson (1925) has reported 

 that in Echium plantagineum, a 

 member of the Boraginaceae, the 

 first division wall in the embryo 

 sac is oblique, separating a 

 small lateral chamber from a 

 large central chamber. The lat- 

 eral chamber, which has denser 

 cytoplasm, divides first and 

 gives rise to two cells which 

 later show several hypertrophied 

 nuclei (Fig. 141 D-F). The cen- 

 tral chamber is more vacuolate, 

 and the divisions are all free nu- 

 clear, wall formation taking place 

 at a much later stage. 



In Anthericum ra?nosum 

 (Stenar, 19286; Schnarf, 19286) 

 the chalazal chamber is cut off in 

 its usual position just above the 

 small and ephemeral antipodals, 

 but the embryo sac soon gives f ig . 140. Embryo sac of Mitella di- 

 out a lateral outgrowth which phylla, showing cell formation in chalazal 

 advances toward the funicular endosperm chamber. (After Dahlgren, 

 side of the ovule and becomes 19S0 ^ 

 an extremely conspicuous structure (Fig. 141 A, B). 



More remarkable still are the lateral haustoria of Monochoria, 

 a member of the Pontederiaceae (Ono, 1928; Juliano, 19316). The 

 early stages are similar to those in other plants having a typical 

 Helobial endosperm (Fig. U2G,H). The chalazal chamber remains 

 small and has only about half a dozen nuclei or less. But the 



