ot Bs 
cies or families, while others affect representatives of widely 
separated groups. Very soon the question rose whether these 
irregularities ought to be considered as more primitive or as 
more advanced than the normal type. The origin of the Angio- 
sperm embryosac is still utterly unknown and it was hoped 
that some light might be given by the study of ‘abnormal 
sacs“. So gradually the attention became focussed on the pro- 
blem: how to arrange the deviations from the normal type in 
a useful system. 
If only a survey of the material was wanted we should be 
free to choose one or two of the most prominent characteristics 
as a base on which a scheme could be built. Since however an 
insight in phylogenetical problems is wanted, we are bound to 
reckon with all the facts that codperate in embryosac-formation. 
There can be no objection to stating that artificial systems are 
entirely worthless for phylogenetical purposes. A useful system 
of the gametophyte necessarily must be natural. 
We will try to give a complete survey of all atypical em- 
bryosacs and of the various systems in which they are classed 
by different authors. At the same time we will have full oppor- 
tunity of discussing any questions of homologizing of the nuclei 
in the embryosac. 
It is not the intention to give anything but the outlines of 
a natural system. Our knowledge of embryosac-formation In 
most families is still too defective to enter into particulars. 
Therefore those facts of which the systematical value 1s clear and 
which do not present any points for divergence of opinion, Bre 
only mentioned without further dicussion. So for instance whether 
the arrangement of the megaspore cells is } or : OF -:; whether 
the inner one or any of the other three becomes the functioning 
megaspore, whether one or more of these megaspore cells develop, 
ete. are details of systematical interest, for which reference to 
special studies on these subjects will answer. 
Il. LITERATURE. 
0 discuss all literature on the 
It would bring us too far t 
We will confine therefore 
origin of the Angiosperm embryosac. 
