ALLIUM CEPA 



III 



Polyembryony has been observed in this genus, in A. odorum L. 

 Tretjakow (xo), Hegelmaier (6), and Haberlandt (4) report 

 the formation of polyembryos in this species and describe their 

 origin from synergids, antipodal cells, and even from the inner 

 integument of the ovule. Tretjakow found from one to three 

 embryos derived from antipodal cells, with the zygote and some- 



3P 



re- — •- 



Fig. icxd. A-I, principal stages in the embryogeny of Allium ursinum L., showing origin 

 of histogens; /, schematic representation of embryo showing regions figured in detail in /: 

 a c, apical cell ; b c, basal cell ; m and / c, superior and inferior cells derived from b c ; n and 

 «', basal cells derived from i c; o and p, cells derived from n'; q, a quadrant of embryo ; dgn, 

 dermatogen ; ^ /», growing point of stem ; /»^w, periblem ; ^/, plerome; r c, root cap. (Re- 

 drawn after Soueges, Compt. Rend. Acad. Sci.^ 



times the synergid forming additional embryos. Hegelmaier 

 found as many as five embryos in a single embryo sac, one being 

 derived from the zygote, one from the synergid, two from antipodal 

 cells, and one from the inner integument. If the usual sequence 

 of reduction divisions had occurred, this would result in haploid 

 embryos, derived from the synergid and the antipodal cells; and 

 diploid embryos from the zygote and inner integument. It appears 

 that the embryos in investigated cases are diploid (16 chromo- 

 somes); and Haberlandt has suggested that this is the result of a 



