646 MINNESOTA BOTANICAL STUDIES. 



present paper were made from sections stained with aniline- 

 water-safranin or acid fuchsin. 



At the present time the material at hand is insufficient for the 

 full demonstration of certain points, especially in the develop- 

 ment of the embryo-sac. Therefore, the present paper will be 

 limited to a discussion of the embryogeny, the development of 

 the embryo-sac and the cytology of reproduction being reserved 

 for future treatment. 



RESEARCH. 



The embryo-sac is ovoid at its micropylar end and tapers down 

 to a narrow attenuation which extends deeply into the nucellus. 

 As the embryo-sac matures the nucellar tissue directly in con- 

 tact with it begins to break down. There also appears in 

 the antipodal region a club-shaped cellular structure which 

 obliterates the lower portion of the sac (Figs, i and 2). The 

 precise origin of this peculiar antipodal body remains yet to be 

 determined. To facilitate description the embryogeny may be 

 considered in a series of stages. 



Stage A. Spherical stage. The young embryo is usually 

 found in the upper end of the embryo-sac among the debris re- 

 sulting from the disintegration of the synergidas. The sur- 

 rounding protoplasm makes it difficult to observe the first 

 division of the oosperm and at the present time the youngest 

 embryo which can be described with certainty is one in the 

 eight-celled stage represented in Fig. 3. As seen here the embryo 

 is nearly spherical, no suspensor being evident, although there 

 may be one present but obscured by the disorganizing synergid 

 " a." This is not probable, however, judging from the position 

 of the first wall in the segmenting embryo. If a suspensor cell 

 is cut off at all, it very early loses its identity as there is no 

 evidence of it in embryos of the age represented in Figs. 

 4-6. Cell division apparently takes place uniformly through- 

 out the embryo, the result being the building up of a spherical 

 body (Figs. 4-7). The embryo retains its spherical shape until 

 composed of several hundred cells. At about this time the 

 nucellar tissue in the micropylar end of the ovule has entirely 

 broken down, so that the embryo now lies in a cavity which is 

 bounded by the inner integument of the ovule. Simultaneously 

 with the division of the embryonal cell the endosperm nucleus 

 divides and the young embryo is soon surrounded by endosperm 



