57 
and the chalazal. group may suffer from a decrease in the 
number of nuclei. Among Orchidaceae these divergent lines of 
development are even met with in the same family. In some 
of the species the micropylar group is still quite normal, the 
chalazal one being affected by reduction in the number of 
nuclei; in other species the micropylar end too never reaches 
the four-nucleate stage. 
Our method of treating the various sections (megaspore- 
formation — micropylar group — chalazal group) of the 
gametophyte as morphological units, capable of following in- 
dependent lines of development, proved to be a real progress, 
in so far at least as closely related species are no longer scat- 
tered all over a system. In this respect our outlines show 
distinct advantages on Courrr’s, Ernst’s, Daaucren’s and I[sut- 
KAwa’s schemes. 
Especially the application of the idea to the 16-nucleate em- 
bryosacs has been fruitful. These sacs are no longer a type of 
their own, but are considered as either of bi- or of tetraspori- 
cal origin. A fully developed tetrasporical sac should be 32- 
nucleate, each megaspore developing a “micropylar* and a 
-“chalazal* group. Both however can be subject to reduction 
conformable to the possibilities, worked out and illustrated in 
figures 5—7. Several of these reduction types can be 16-nucleate. 
Of course full development of a bisporical sac also leads to 
a 16-nucleate embryosac. 
Up to the present moment the Angiosperm embryosac has 
held a wholly isolated position. Its origin could not be traced 
and its analogies among Gymmnosperms were dark. A gap in 
phylogenetical knowledge on such an important point, necessa- 
rily has led to numerous suggestions. None of these, however, 
passed the hypothesis stage. It apparently depends in the main 
on the author’s preference for a certain theory on the origin 
of Angiosperms, which type of embryosac he will call the most 
primitive one. It must be admitted that this is not the right 
way of settling the question, using phylogenetical speculations 
