366 The Ohio Naturalist. [Vol. Ill, No. 4, 



which degenerate for the enlargement of the sac which occupies 

 the entire inner zone in the eight-celled stage (Fig. 7). The 

 walls of this inner zone were so delicate that it was difficult to 

 get good preparations of the eight-celled stage. The outer zone 

 is made up of thicker walled cells, which are more permanent and 

 which are in more or less regular rows, which radiate from the 

 inner zone. The inner zone is connected with the micropolar end 

 of the ovule by two or three rows of elongated cells, which 

 degenerate to form the path for the pollen tube ( Figs. 5 and 23). 

 After fertilization the part of the nucellus projecting through the 

 micropyle degenerates and the integuments come together at that 

 point. 



Lyon-'' describes an enlargement of the ovule similar to that in 

 Euphorbia corollata, except that there is no zone-like structure, 

 and the cells which break down for the passage of the pollen tube 

 are larger and looser than the surrounding tissue. 



After the conjugation of the polar nuclei the sac enlarges on 

 one side and at right angles to its long axis (Fig. 24). The 

 endosperm nucleus passes down into this pocket, divides and event- 

 ually forms a peripheral endosperm (Fig. 18). One case was 

 observed where the endosperm nucleus had failed to divide, 

 although the embr^-o was in its five-celled stage. At the lower 

 end of this newly formed pocket a mass of endosperm is formed, 

 which probably hastens the absorption of the nucellus at that 

 point ( Fig. 19 ). At this time the egg has enlarged considerabl}'^ ; 

 the s^-nergids remain about the same size and disappear very 

 early ; in only one case was a sj-nergid observed to persist until 

 after the formation of the first transverse wall in the embryo. 

 By the enlargement of the sac in the new direction the antipodals 

 are left in a small pocket (Fig. 24^); they degenerate, sometimes 

 by fragmentation, and eventualh' disappear. 



The pollen tube was observed a number of times, always fol- 

 lowing the canal formed by the absorption of the cells previously 

 described, but in no ca.se was I able to observe the act of fertili- 

 zation. 



EMBRYO. 



The fertilized egg divides by tran.sverse wall, the lower cell 

 enlarging into a large ba.sal cell (Fig. 8). The upper cell now 

 divides by transverse division (Fig. 9). This is followed by a 

 series of transverse divisions, the order of which I could not 

 determine, resulting in a filamentous embryo of five, six or seven 

 cells, with one large basal cell (Figs. 19, 11, i2j. When the 

 embryo has reached this condition the cell next to the upper cell 

 divides by a longitudinal wall (Fig. 13). The cell next below 

 now divides in a similar manner, while the two cells next to the 



'•' Florence May Lyon. A Contrihiition to the Life Ilistorv of Kiiphorbia corollata. 

 Bet. Gaz. 25, 6. iS98. pp. 418-426. 



