Ai>RiL 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 365 



is sometimes developed, which, on the division of the anti- 

 podal nucleus, takes up a position between the two newly 

 formed nuclei (fig. 23). 



After a time division of the two nuclei in the embryo- 

 sac (figs. 16, l7*-°, 19) takes place, and thus four nuclei 

 are formed (figs. 20-23). In fig. 20 we see that the 

 antipodal nucleus is both the most advanced in division 

 and that it gives rise to a much larger diaster than 

 the micropylar nucleus. In several sections I have noticed 

 in the embryo-sac, both at this stage (fig. 23) as also after 

 the formation of eight nuclei, spherical colloid-like masses 

 not stained by hiiematoxylin {H. B.), the origin of which I 

 was unable to make out. In fig. 24 the four nuclei within 

 the embryo-sac are undergoing division to give rise to eight 

 nuclei. Similarly as in fig. 20 we notice how the two anti- 

 podal nuclei are more advanced in division than the two 

 micropylar ones, and that again of the two antipodal ones, 

 the one next the plerome has advanced the furthest. The 

 centre of the sac is occupied by a large vacuole, and there is 

 no protoplasmic connection between the apical or micropylar, 

 and the basal or antipodal halves of the embryo-sac. 



One diaster {syn) is placed at the very apex with its long 

 diameter at right angles to the long axis of the sac ; it is 

 again seen in a later stage of division in fig. 25''*, and after 

 completion of the division syn, in figs. 25^ 26, 27, 29^ 

 The two cells arising from this diaster have been called by 

 Strasburger, the synergidee, as they were believed to play 

 an important part in conveying the male fertilising-element 

 of the pollen-grain to the egg-cell. The second micropylar 

 diaster {ov. fig. 24) is placed obliquely, and its function is to 

 give rise to two nuclei, one of which surrounds itself with a 

 mass of protoplasm, and forms a thin membrane on the out- 

 side of this protoplasm, and thus shuts itself off from its 

 sister-nucleus. This third cell arising in the micropylar 

 half of the sac and provided with a definite membrane, 

 develops into the egg-cell or ovum {ov. figs. 25^ 25'', 26*, 28, 

 30, 31). The sister-nucleus of the egg-nucleus lies imbedded 

 in a mass of protoplasm (m.p.c, fig. 25"*), and does not 

 surround itself with a definite membrane, and has therefore 

 to be regarded as the nucleus of a free or primordial cell. 

 The latter is bounded above by the two synergidie and the 



