﻿MICH ELL — RICH A RDIA AFRICAN A 



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ance of the rudiment of the outer integument, the nucleus of this 

 cell goes into synapsis. Fig. 1 shows the spireme loosening itself 

 from the synaptic knot. The synaptic knot in Richardia is a 

 very tight one, and in many ovules in this stage no trace of the 

 spireme could be detected emerging from it. Fig. 2 shows a further 

 stage in the heterotypic division, 12 bivalent chromosomes being 

 arranged on the equatorial plate. The homotypic division follows, 

 thus giving rise to a row of 4 megaspores. Fig. 3 shows stages in 

 the anaphase of this division. In the nuclei represented in this 

 figure it is interesting to note that in the upper nucleus the two 

 halves of one chromosome have not separated, but have remained 

 attached by one end. As a rule sluggish divisions of this type were 

 not observed. 



Of the 4 megaspores, only the lowest gives rise to the embryo 

 sac. Fig. 4 shows an ovule in which the uppermost megaspore is 

 beginning to degenerate. In certain cases in which the uninucleate 

 embryo sac is a little larger than the one in this figure, only the 

 remains of 2 megaspores could be detected. It is possible that in 

 these cases only 3 megaspores were formed, although none of my 

 preparations of stages before degeneration shows fewer than 4 

 megaspores. 



Gow (7) states that the spore mother cell develops directly into 

 the embryo sac and that a row of megaspores is not formed. In 

 my material I found that a row of megaspores is invariably formed, 

 and in no case is there anything to lead one to suppose that the 

 embryo sac has originated directly from the megaspore mother cell. 



The development of the embryo sac is perfectly normal. In 

 the majority of cases there is a marked polarity. Fig. 5 shows the 

 first division in the embryo sac. In the section represented, only 

 2 of the degenerating megaspores are to be seen, but a third is 

 present in the next section. Fig. 6 shows the binucleate stage of 

 the embryo sac, and fig. 7 the 4-nucleate stage. Fig. 8 represents 

 the division of these 4 nuclei. It is unfortunate that this was the 

 only case obtained in which the 4 nuclei were dividing, as the 

 polarity so generally met with is absent, and it is not known whether 

 this is the usual state of affairs or not. In subsequent stages shown 

 m my preparations the embryo sac is markedly bipolar. 



