Igr2] PFEIFFER—LEITNERIA 201 
There is a large development of parietal tissue in the ovule, 
as many as thirty layers of cells lying above the embryo sac at 
its maturity. 
Practically all megaspore mother cells were in synapsis on 
March 22. 
A linear tetrad of megaspores was evidently formed. 
By April 7 practically all embryo sacs showed the eight- nucleate 
female gametophyte. 
After fertilization the endosperm nucleus divides repeatedly, 
giving rise to a large number of free nuclei before the division of 
the fertilized egg occurs. 
After wall formation in the endosperm begins, there is an 
extremely regular centripetal growth of tissue. 
The first division of the fertilized egg may be longitudinal or 
_ transverse; in either case a massive suspensor is formed. 
The young embryo is a pear-shaped mass which is composed of 
hundreds of cells before the cotyledons appear. 
In the root tip of the embryo, calyptrogen, dermatogen, and 
plerome arise from a common meristematic group of cells. 
The growth of the seed is very rapid, and at maturity it con- 
tains a large, flat, dicotyledonous embryo, a thin layer. of endo- 
sperm tissue, and a few layers of perisperm cells. 
The seed coat is formed mostly from the outer integument, the 
inner integument contributing only its innermost layer of cells. 
The morphology of Leitneria is not such as would make it 
possible to place it definitely in any of the families of the Archi- 
chlamydeae, but, in common with other Amentiferae, it suggests 
the possibility of the derivation of Amentiferae from such forms as 
one finds among the gymnosperms which have compound strobili. 
The author is indebted to Professors Joun M. CouLtTer and 
CHARLES J. CHAMBERLAIN, under whose direction this work was 
done, and to the staff of the Missouri Botanical Garden of St. Louis 
for aid in collecting material. 
THE UNIVERSITY OF CHICAGO 
