1914] MANEVAL—MAGNOLIACEAE 9 
on the other hand, sees here an omission of tetrad formation and 
one more than the usual number of divisions in the germination of 
the megaspore to the embryo sac. He therefore considers the 
16-nucleate sac as an older, or at any rate an independent, form 
of embryo sac, not derived from the 8-nucleate type. These two 
views, then, are directly opposed to each other. 
With respect to the nature of the 16-nucleate embryo sac of 
Peperomia, CAMPBELL (4) and JOHNSON (15, 16), as is well known, 
have arrived at opposite conclusions. CAMPBELL says: “‘ Peperomia, 
in regard to the embryo sac, probably represents the most primitive 
form yet discovered among the angiosperms... . . Peperomia 
offers a basis for an explanation of the homologies of the embryo 
sac.” JOHNSON, a little later, after studying several genera of 
Piperaceae, maintained that the peculiarities in Peperomia are of 
secondary origin.. The latter view is supported by Brown (3) 
who, in Peperomia sintenisii and P. arifolia, finds that at the first 
two divisions of the embryo sac mother cell typical reduction of 
chromosomes occurs; and also that during these divisions the 
nuclei are separated by evanescent cell walls. So he concludes 
that these phenomena seem to indicate that the sac is a compound 
structure derived from the nuclei of four megaspores, the primary 
sac nucleus being a mother cell rather than a megaspore. 
Reference has been made to CouLTER’s view that while the 
genesis of the ordinary angiospermous embryo sac from the mega- 
spore mother cell involves 5 divisions, the essential part of the 
process is found in the first two divisions which, so far as we know, 
are necessary if fertilization is to occur. BROWN (3) maintains 
that we cannot make chromosome reduction the sole criterion of 
megaspore formation, and adds as another distinction that while 
a division giving rise to megaspores is characterized by a cell wall 
or a cell plate, the first division of a megaspore is not accompanied 
by a cell plate. Quite lately SmrrH (27) has pointed out that 
this distinction does not hold in the case of Clintonia, where, at 
the first division of the megaspore nucleus, a cell plate appears, 
and SmirH infers it will not hold for certain other cases. 
Sufficient emphasis, it seems to the writer, has never been given 
to the fact that while the anomalous types of embryo sac are as a 
