20 
polarisation is, has never been subjected to a special study. 
Its origin, its inducing factors, its function, etc. are entirely 
unknown, which is the more remarkable since everyone who 
has ever studied the development of an embryosac must be 
familiar with the process. It goes beyond the scheme of this 
paper to expatiate on questions connected with its meaning. 
From our point of view it will do to state that the process 
goes on in all embryosacs in absolutely the same way. The 
formation of the well known large central vacuole is the most 
prominent phenomenon that accompanies polarisation and there- 
fore worth our special attention. In the normal eight-nucleate 
sac, sprung from a “row of four* no trace of vacuolation’) is to 
be seen during megaspore-formation. Protoplasm remains a ho- 
mogenous mass until the development of the embryosac (mega- 
spore) begins. Then vacuolation commences as a group of small 
vacuoles which soon results in the usual large central vacu- — 
ole. This process passes with such rapidity that even the 
two-nucleate stage could never be found without the typical 
large vacuole, which separates both nuclei, indicating them 
as primary micropylar and primary chalazal nucleus. This 
normal course of vacuolation is so common that most authors 
do not even mention it. As a matter of fact polarisation 
and vacuolation of the embryosac are mostly left out of 
discussion, only. few authors indicating them. Sometimes even 
their figures are but outlined, all information on the subject 
thus lacking. Mopimewskr (1909) seems to have felt its signifi- 
cance when saying: “Man musz aber womoglich nicht nur 
dieses Merkmal (die Zahl der Kerne) sondern auch die Hohe 
der Symmetrie und die Polaritat des Embryosacks in Betracht 
ziehen. Dan wird man vielleicht imstande sein, einige Anhalts- 
punkte zu gewinnen.* No attention at all, however, is paid to 
these words. A thorough study of the publications (including 
their figures!) on abnormal embryosacs will show the correct- 
ness of Mopiewsk1’s remark and the fundamental significance 
hy It is not the intention to give any opinion on the origin and formation of 
the vacuoles. Here and in the following the word “vacuolation* is only used for 
indicating the appearence of the central vacuole. 
