‘THE EMBRYOSAC OF VITTADINIA 
BY 
BJ. T. PALM. 
The female gametophyto in the Compositae shows, as has 
long been known, a remarkable display of variations in structure, 
especially in its antipodal region. More recently deviations from 
the pred ting normal type of development have been 
described. 
A summary of our knowledge up to the present regarding 
the various modes of gametophyte development in Compositae 
may be useful in interpreting the account given beneath of the 
embryosac formation in Vittadinia. 
Three main types of gametophytes may conveniently be 
distinguished, based on the number of megaspores involved in 
the formation of the gametophyte. For a detailed discussion of 
this point in Angiosperms in general see the writers “Studien 
tiber” Konstruktionstypen und Entwicklungswege des Embryo- 
sackes der Angiospermen (p. 201—232). 
The normal type includes those instances where one of the 
four megaspores gives rise to the definite embryosac; these 
megaspores may be separated from each other by walls or remain 
in a syncytial condition. 
When the megaspores are separated from each other by walls, 
by far the most common condition, the chalazal megaspore, — 
the one farthest from the micropyle, — develops into the embryo- 
sac. This applies to most of the Compositae as well as to most 
Angiosperms. Sometimes any one of’ the megaspores, as in 
Aster nova-angliae, A. Pattersoni, Chrysanthemum Leucanthenum, 
Senecio sagittatus (= Emillia sagittata) (Pam 1914a, 1915) may 
