THE EMBRYO 



219 



phenomenon as many may have supposed. The cases on record 

 are already so numerous that only an exhaustive study of the 

 literature would make it safe to venture an estimate of the 

 number. Since in nearly all the cases described this phenome- 

 non is rare rather than habitual, it is probable that under con- 

 ditions not yet understood a large number of plants may exhibit 

 polyembryony occasionally. 



FIG. 106. Embryos in parthenogenetic species of Alchemilla. A, A. sericata, one par- 

 thenogenetic embryo from egg and one from synergid, the other synergid breaking 

 down; the two polar nuclei and antipodal cells also shown: x 284; .Z?, A. pastoralis, 

 showing one synergid partly disorganized, one embryo of four cells from unfertilized 

 esrir, one embryo from nucellus, two polar nuclei and one synergid nucleus forming 

 group at middle of sac, also three disorganizing antipodal cells; x 190. After 



MURBECK. 80 



The scattered literature of the subject is admirably sum- 

 marized by Ernst 69 in his presentation of polyembryony in 

 TuUpa Gesneriana. The following synoptical statement is 

 taken from Ernst, and supplemented by the more recent addi- 

 tions. Tn case the same form is treated in several accounts, 

 there is no attempt to cite all of them or even the first refer- 

 ence, but a selection is made of those citations that direct to 



