April 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 367 



the cells nearer the base of the ovule are older, more resisting 

 and better fed than those at the apex. At the time of 

 maturation we find the ovule (fig. 30) to consist of the 

 ilermatogen, the remains of the nucellar periblem-cells and 

 tlie enormously increased parasitic sporocyte or embryo-sac. 



Let lis return to the two groups of eight cells within the 

 sporocyte- sac. The synergidne at the time of their formation 

 (fig. 25", syn) are attached by a broad base to the most 

 apical part of the embryo-sac, are almost isodiametric and 

 enclosed in a firmer wall than the ovum or egg-cell. Very 

 soon, however, the synergidal cells change their shape, due to 

 growth taking place parallel to the long axis of the ovule 

 (fig. 25''), and still later one vacuole is formed in the basal 

 end of each cell (fig. 26, sijn). To what extent the synergidse 

 may elongate can be gathered from fig. 29" ; (the elongation 

 and vacuolation are not seen in figs. 27, 30, 31 as the lower 

 ends of the synergid?e are lying in the next serial sections). 



The egg-cell is placed on a slightly deeper plane than the 

 synergidse (figs. 25", 28, ov) with its nucleus and the greater 

 part of its protoplasm towards the antipodal end, the micro- 

 pylar end being occupied by a vacuole. Thus we have, as has 

 been pointed out by Strasburger long ago, in the ovum or 

 egg-cell a condition the very reverse of that occurring in the 

 synergidffi ; a difference well seen in fig. 28, showing one 

 synergida {syn) with a vacuole in its antipodal half, and an 

 ovum (ov) with a vacuole in its micropylar half. How we 

 may account for this phenomenon, I shall attempt to explain, 

 after I have alluded to the fate of the two primordial cells. 



The micropylar [m.]). c) and the antipodal [a.p. c) cells are 

 at first not connected by protoplasmic strands (fig. 25*, 25'^), 

 but later protoplasmic connections are established (figs. 26, 

 27", 28, 29", 30, 31), and the nucleus of the antipodal cell 

 travels towards the nucleus of the micropylar cell, both nuclei 

 unite and give rise to what Strasburger has called the 

 secondary nucleus of the embryo-sac. Thus a protoplasmic 

 connection is established between the micropylar and the 

 antipodal halves of the embryo-sac. To return to the 

 synergidse and the ovum : — It has been pointed out how the 

 enlargement of the embryo-sac leads to a degeneration of the 

 nucellar periblem-cells, a degeneration which commences at 

 the apex of the ovule and then gradually spreads towards its 



