23 
When marking vacuolation, differences will be noticed in 
the early stages of embryosac-formation in e.g. Lilium, Glun- 
nera and Peperomia, and they will be recognised as being of 
resp. mono-, bi- and tetrasporical character (Fig. 2). Likewise 
the peculiar number of eight fusing nuclei in Peperomia (Fig. 9) 
and of seven in Gunnera (Fig. 11) loses its mystery. It is not 
necessary to supply further examples here; the hypothesis’ 
working capacities will become more and more clear in the 
following pages. 
2°. [In the two-nucleate stage of a normal embryosac the nucler 
are always separated by the large central vacuole (the embryosae is 
polarised). 
The significance of this central vacuole for homologising pur- 
poses is plain. It provides us with means to distinguish the 
nuclei of the micropylar end from those of the chalazal end. 
There is no difficulty whatsoever in distinguishing the pri- 
mary micropylar nucleus and the primary chalazal one. Only 
few authors however have realized the significance of this pola- 
risation. As we will point to it often later on, one instance 
will do for the moment to illustrate its extraordinary value: 
In Onagraceae all four nuclei of the mature sac are found 
at the micropylar end. The likewise four-nucleate Plumbago sac 
shows two nuclei at each end of the central vacuole. In the 
first case all nuclei are of micropylar origin, in the second one 
two are micropylar and two chalazal. Though both sacs are 
four-nucleate it is undoubtedly a mistake to homologise these 
two. From the very beginning of their development they are 
plainly different. 
Megaspore-formation. 
Normally a “row of four‘ is formed, one of which becomes 
the functioning megaspore, Whether the arrangement of these 
cells is:? or : or .:-, and whether the inner one or any of the 
other three becomes the functioning megaspore '), and even 
1) Discussion and complete literature by Pam (1915, p. 110). 
