14 
Isnrkawa (1918) lately published a scheme which from a 
phylogenetical point of view is certainly to be marked as a 
distinct progress. He no longer sticks to one or two rather 
voluntarily chosen moments in the development of the embryo- 
sac, but he tries to reckon with the other facts as well. His 
scheme (Ann. of Bot. 32, p. 305, Fig. XI) not only deals with 
the number of divisions and with the number of megaspores 
which join in embryosac-formation, but also pays attention to 
the origin and to the number of nuclei in the full-grown sac. 
So it really contains some necessary elements for the building 
up of a natural system. 
When put into practice however its usefulness is rather 
limited. It meets our present knowledge of embryosacs, but is 
not planned broadly enough to include further possibilities. It 
gives an insight in the author’s views on homologies, but it 
does not give a valuable system. It is meant to give much, 
but it is worked out confusedly. Perhaps that is the reason why 
all harmony with the sporophytic system is absolutely lacking. 
Objections against Coulter's principles. 
As the most succesful arguments against the view, the 
development which of we just finished sketching, the following 
has been brought forward: 
1°, Against the assumption that megaspore-formation cannot be 
shortened and always must be preceded by two divisions, 
was moved the fact that the sporogenous tissue has gra- 
dually been restricted from an elaborate tissue among Gym- 
nosperms to only one cell in most Angiosperms. There is 
no reason why this tendency to shorten the gametophyte- 
generation should have stopped there. On the contrary we 
might expect this tendency to go on and affect megaspore- 
formation. It gives a natural explanation of the reduction 
series as demonstrated in the “row of four‘, “of three*, 
“of two‘, “no row at all.é 
. Against the assumption that megaspore-formation should be 
determined by chromatine-reduction, was moved Moursrck’s 
(1901) discovery of the embryosac-development in Alche- 
bo 
° 
