THE EMBRYO 



305 



a filament of variable length whose lower portion gives rise to the 

 embryo proper. 



Ernst and Schmid (1913) report that in Rafflesia patma the ter- 

 minal cell of the two-celled proembryo undergoes a transverse 

 division to form two cells, each of which divides longitudinally. At 

 the same time the basal cell divides vertically. At this stage the 

 proembryo enters into a period of rest although cell divisions con- 

 tinue to take place in the endosperm. When development is 

 resumed, only one or two more divisions take place in the embryo. 



B C D E 



Fig. 176. Development of embryo in Ranunculus ficaria up to time of shedding 

 of seed. (After Soueges, 1913.) 



In Aeginetia indica, a member of the Orobanchaceae (Juliano, 

 1935), the zygote remains dormant for a considerable time after 

 endosperm formation has commenced. The first two divisions are 

 transverse, resulting in a short filament (Fig. 175A-C). The nar- 

 row suspensor cells soon become crushed and disorganized, and the 

 two terminal cells divide to give rise to a small globose embryo 

 without any differentiation into a radicle, plumule, or cotyledons 

 (Fig. 175D-I). Figure 175 J" shows a longitudinal section of the 

 mature seed with the spherical embryo surrounded by a layer of 

 endosperm cells. 



Embryos of an extremely reduced type are also known in the 

 Burmanniaceae (Ernst and Bernard, 1912). In Burmannia coe- 

 lestis (Fig. 175K-N) the basal cell of the two-celled embryo divides 

 by a transverse wall and the terminal cell divides by two vertical 

 walls to produce a quadrant. Development seems to be arrested 

 at this six-celled stage. 



