58 
as basis for a system, instead of systematics as basis for phylogeny. 
The present study did not succeed in throwing more light 
on the origin of the Angiosperm sac. It has led us to the view 
that all embryosacs with an abnormal number of nuclei are 
derived from the normal eight-nucleate type. This conception 
of the 8-nucleate sac as the most primitive one fully agrees 
with the actual conditions, for it is met with in all families 
at the bottom of the natural system. On this point the phylo- 
genetical value of our results is purely negative: it leads us 
to reject all theories on the origin of Angiosperms, which are 
founded on the “primitive character‘ of the 16-nucleate em- 
bryosac or of the embryosac with an increased number of 
antipodals. 
VI. FACTORS WHICH MAY ACCOUNT FOR THE ANOMALIES 
IN EMBRYOSAC-DEVELOPMENT. 
The reduction in the number of megaspores (‘row of four*, 
“row of three“, “row of two‘, “no row at all*), in the number 
of micropylar nuclei (four, three, two or one nucleus), in the 
number of chalazal nuclei (four, three, two, one or no nucleus), 
they all succesfully can be brought back to the same causes. 
First of all the process of shortening the sex generation must 
be mentioned. In most Angiosperms the sporogenous tissue has 
been reduced to one cell only. So the next step on this way 
necessarily must affect megaspore-formation and embryosac- 
development. 
Secondly there is the usual desintegrating and final suppres- 
sion of non-functioning tissues. This is too well-known from 
sporophytic conditions to need any further commentary. Its 
application to the megaspore-formation and embryosac-develop- 
ment will meet no objections. 
The reduction in the number of megaspores probably is caused 
by both processes. Normally three of the spores are seen des- 
integrating. A total suppression should be an anticipation oD 
this degeneration. ; 
The reduction at the chalazal end too may be influenced by 
