340 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



lateral position as regards the synergidse, which is the posi- 

 tion of the ^^^ in Sesleria also (Fischer). The synergidae 

 are flask-shaped and do not appear to contain vacuoles. 

 The egg-apparatus increases greatly in size but shows no 

 other change up to the time of fertilization. 



The upper polar nucleus moves to meet the lower polar 

 nucleus in the region of the antipodal nuclei (figs. 21 and 

 22) . The two nuclei then move towards the ^^^ and remain 

 in close proximity to it, in the protoplasmic bridge that con- 

 nects the egg-apparatus and the antipodals. The polar 

 nuclei do not fuse until about the time of the fertilization of 

 the ^g^- The exact time was not determined. The nu- 

 cleoli of the polar nuclei are the largest in the embryo-sac 

 and with the ordinary staining reagents become deeply 

 colored. The peculiar behavior of the polar nuclei of the 

 oat does not agree with that in the grasses examined by 

 Fischer; but Koernicke indicates that some such action of 

 the polar nuclei occurs in Triticum, as he states that the 

 two polar nuclei move towards each other. The sides of 

 the polar nuclei that are in contact with one another are 

 flattened, and each cell retains its delicate cell-wall up to 

 the time of fertilization, when they fuse to form the endo- 

 sperm nucleus. The time of the fusion of the polar nuclei 

 of the oat appears to be the same as that in the wheat. 

 There is no rule as to which side of the polar nuclei will 

 come in contact, so that a line separating them may be 

 parallel to the long axis of the embryo-sac, at right angles 

 to it, or it may be at any angle between the two. The 

 endosperm nucleus is imbedded in a dense strand of proto- 

 plasm which connects the antipodals and the ^gg, and 

 strands radiate from this to the walls of the embryo-sac. 

 This last is especially true of the younger sacs, the proto- 

 plasmic threads disappearing in the older stages. The 

 protoplasmic bridge persists however until the antipodals 

 disappear. 



The embryo-sacs of all the grasses that have been studied, 

 except Melica (Fischer), show a multiplication of the anti- 

 podal cells. This phenomenon has also recently been 



