44 
Lewsk1 1908, Ernst 1908, Samuers 1912) agree on most of the 
important points. The first division of the embryosac-mother- 
cell nucleus is not followed by wall formation and from the 
figures it is clear that the large vacuole is formed at the four- 
nucleate stage. From what is said in a previous chapter we 
must conclude that the Gunnera sac reprents a bisporic con- 
dition, polarisation leading us to homologize the four-nucleate 
stage with the two-nucleate one of normal sacs. Both mega- 
spores of the embryosac come to full development, thus giving 
rise to two micropylar and two chalazal groups of 4 nuclei 
each. In the mature sac one of the micropylar groups (the 
egg apparatus) is to be found at the top, both chalazal groups 
come together at the bottom, while the second micropylar 
group, in which cell formation is omitted, fuses with the three 
polar nuclei of the other groups. This agrees with the figures 
published by the different authors, showing an ordinary egg- 
apparatus, six antipodals and seven fusing nuclei. Special attention 
might be called to the fact that this explanation of the Gun- 
nera embryosac, based on the vacuolation, results in a reasonable 
explanation of the puzzling number of seven fusing nuclei. The 
development corresponds to CC—1l—la (fig. 11, p. 43). 
Plumbago species, investigated by Danieren (1915, 1916) all 
showed a four-nucleate sac. The two-nucleate stage is clearly 
polarised, both the primary micropylar and the primary cha- 
lazal nucleus giving rise to a group of two nuclei, viz. an egg, 
two polars and one antipodal, which corresponds to D-IIIb-3a. 
Ceratostigma (DanierEN 1916) normally develops in the same 
way. Occasionally however the antipodal degenerates. In Plum- 
bagella (Dauteren 1915, 1916) this desintegration is fixed, the 
full-grown sac never containing more than three nuclei: 
D-Ilb-3az. 
Pyrethrum parthenifolium var. aureum (Patm 1915) supplies 
another instance of a bisporic sac. In the two-nucleate stage 
plasm in still homogenous, vacuolation immediately following 
the next division. As in Gunnera, here too, the bisporical cha- 
racter is accentuated by the direction of the spindles and by 
the early stages of vacuolation. “Bei der zweiten Teilung im 
