61 
to be accepted without further confirmation, and two more 
recent studies (Pacx, 1907 and Kusano, 1915) in which however 
figures are probably misinterpreted. 
I. 
no 
Co 
VIII. SUMMARY. 
Several attempts have been made to classify the various 
types of Angiosperm embryosacs. These systems are based 
either on the number of divisions between embryosac- 
mothercell and egg (Cov.rer) or on the number of nuclei in 
the full-grown sac (Ernst). They are wholly artificial and 
therefore without any phylogenetical value. 
. The female gametophyte is no morphological unit, but a 
complex, as well as the sporophyte. A natural system there- 
fore presupposes thorough and detailed knowledge of mor- 
phology. It has to reckon with the following processes as 
probably independent lines of development: 
Chromatine reduction. 
Megaspore formation. 
Polarisation. 
Development of a micropylar group of nuclei. 
Development of a chalazal group of nuclei. 
. Chromatine reduction usually accompanies the first divisions 
of the embryosac-mothercell. Sometimes (in apogamous spe- 
cies) it is omitted, which proves that it is not identical 
with megaspore-formation. 
Polarisation is a function of the developing megaspore 
(embryosac). It does not accompany megaspore-formation, 
but megaspore-development. It commences as soon as me- 
gaspore-development. begins. It therefore provides us with 
means of recognising megaspores, even when two or four 
megaspores are lying in the same cell: as long as plasm 
remains homogenous spore-formation 1s still going on, as 
soon however as polarisation (vacuolation) commences we have 
to do with germinating spores. Moreover a large central 
vacuole enables us to tell the nuclei of the chalazal group 
from those of the micropylar group. 
