62 
Megaspore formation usually leads to a “row of four.* 
Occasionally however only three or two megaspores are 
formed, or even the embryosac-mothercell itself is seen 
functioning as a megaspore. The omission of cell walls 
during spore formation may affect the number of nuclei in 
the mature embryosac: four germinating megaspores in 
the same cell give rise to a tetrasporical, three to a tri- 
sporical and two to a bisporical sac. We are forced to admit 
theoretically: 9 types of monosporical, 5 of bisporical, 2 of 
trisporical and 1 of tetrasporical sacs. The further develop- 
ment of the megaspores must be considered as wholly in- 
dependent from their formation. 
Development of the micropylar group of nuclei. Normally it 
results in a group of four nuclei. Sometimes however the 
number has been reduced. Theoretically this reduction can 
go down to there being only one nucleus left, the primary 
micropylar nucleus or even the megaspore itself thus assuming 
the egg-function. 
Development of the chalazal group of nuclei. Here all stages 
of the reduction series may be met with, from the usual 
four down to total suppression of the entire group. Even 
when nuclei are still formed their desintegration is of 
common occurence. On the other hand a secondary increase 
in the number of nuclei sometimes has been reported. 
. A few, most probably incorrect, records excepted, all publi- 
cations on abnormal embryosacs seem to confirm this con- 
ception of considering the Angiosperm embryosac as @ 
morphological complex. 
Another confirmation is to be found in its systematical 
value. Relationships are established by the study of the 
gametophyte as well as by the study of the sporophyte. Espe- 
cially the application of our views to 16-nucleate sacs has 
been fruitful. They are no longer a type of their own, but 
of bi- or tetrasporical origin, each one of their megaspores 
being open to the deviations, which we have worked out 
with regard to the monosporical sac. 
6. The reduction processes by which megasporeformation, micro- 
rs 
= 
