THE EMBRYO-SAC OF AGLAONEMA 



I I I 



embryo shown in PI. IV. fig. 41. There is a large basal cell 

 which may be considered as a suspensor, while the upper part 

 of the embryo is composed of an oval mass of similar cells 

 with no evidence of a differentiation of the organs. 



Text-figure i, B, represents a sac of about the same age as 

 that figured in 41, but the embryo has quite a different shape. 

 This embryo looks as if the first division wall had been longi- 

 tudinal instead of transverse, or as if one of the synergidae 

 had also divided and contributed to the growth of the embryo. 



Text-figure i, A, shows a similar stage in A. coininutatum. 



Fig. 2. — A, longitudinal section of a young seed of Aglaonenia niodestniit, x lo. 

 The embryo shows the root, r. , and the cotyledon, cot. ; en., endosperm ; 

 per., perisperm. The arrow indicates the micropyle. B, an older seed. 

 The embryo fills the embryo-sac, and the second leaf, /.-, is developed ; St., 

 the stem region. C, the root-apex, x 60. D, the apical region of the 

 stem, X 60. 



The curvature of the embryo-sac is especially noticeable in 

 this species, and in the specimen figured the embr}'o lies 

 near the middle of the sac close to the concave side. It is a 

 mass of perfectly uniform cells with no trace of a suspensor 

 nor any evidence of the organs found in the older embryo. 

 The growth of the embryo is now very rapid and it encroaches 

 upon the endosperm, which is finally almost destroyed by the 

 embryo which finally practically fills the entire cavity of the 

 embryo-sac (text-figure 2). 



The embryo now becomes much elongated, and the end 

 directed toward the micropyle becomes the apex of the first 

 root, while the other end develops into the large cotyledon. 



