i 9 i6] CHAMBERLAIN— STANGERIA PARADOXA 369 



less completely its vacuolated appearance as it is resorbed by the 

 rapidly developing embryo. Before the appearance of cotyledons, 

 the young embryo has resorbed all the cytoplasm and nuclei of the 

 free nuclear region, which becomes an empty shell, maintaining its 

 contour only by the rigidity of the tough egg membrane. All the 

 structures of this region, however, are finally crushed by the back- 

 ward thrust of the suspensor, which is stopped only by the stony 

 coat of the seed. 



Differentiation of cellular region. — Differentiation of 

 the cellular region begins almost as soon as it is marked off from the 

 free nuclear region above it. At first there is seen a differentiation 

 into two general regions: the upper, in contact with the free nuclear 

 region, consisting of larger cells; while the cells of the lower are 

 much smaller, but denser and more numerous (fig. 21). Some of 

 the upper cells, especially in the center, increase greatly in size and 

 become actively haustorial; it is through these that the contents of 

 the free nuclear region pass down to the developing embryo (fig. 23). 



The smaller, denser cells then become differentiated into two 

 regions, the lower consisting of a single layer of large cells which 

 looks like a dermatogen, and above it several layers of small, dense 

 cells (fig. 22). Most of the outer cells become haustorial, especially 

 at the center. These cells partly digest and partly crush the egg 

 membrane, and the young embryo begins to advance into the 

 endosperm (fig. 23). Only a small portion of the egg membrane is 

 ruptured, and the advancing embryo is extremely narrow in com- 

 parison with those of cycads previously described. The region of 

 small, dense cells contributes most of the suspensor and all of the 

 periblem and plerome of the embryo. 



Stages in the development of the body regions of the embryo 

 are still lacking in my material, but will doubtless be found in 

 collections now being made in South Africa. From the mature 

 embryo up to seedlings with several leaves the series is fairly com- 

 plete, and some account will be given at another time in connection 

 with a study of seedlings of other genera. 



This paper, like several earlier papers on cycads, is largely 

 descriptive. Since material is in hand for a fairly complete study 



