218 



MORPHOLOGY OF ANGIOSPERMS 



one normal, one from a synergid, two from antipodal ceils, and 

 one from the inner integument (Fig. 105). It is interesting 

 to note that while polyembryony is so frequent in Allium odo- 

 rum, it has not been observed in other 

 species of the genus. JEegelmaier exam- 

 ined A. fistulosum and A. ursinum, and 

 Elmore 50 made a thorough study of A. 

 cernuum, A. tricoccum, and A. canadense, 

 without discovering a single extra em- 

 bryo, reporting also very small and eva- 

 nescent antipoclals. In parthenogenetic 

 species of AlchemiUa Murbeck 76 found 

 embryos from the egg, from the synergids, 

 from the three antipo- and from the nucellar tissue (Fig. 106). 



In Balanophora elongata and B. glo- 

 bosa fertilization is known not to occur, 

 and both Treub 46 and Lotsy 58 state that the embryo is formed 

 by the upper polar nucleus. In addition to this, a cell in the 

 midst of the endosperm is said to develop into a five to ten- 

 celled " pseud-embryo/' whose significance and history we are 



dal cells; x 116. After 



TRETJAKOW. 36 



FIG. 105. Allium odorum. A, section of ovule with four embryos, one from egg. one 

 from a synergid, ore from an antipodal cell, and one from the Avail ; x 15 ; J2, tAvo 

 embryos, one from egg and one from a synergid: the other synergid someAvhat 

 enlarged and lying between the two embryos ; x 246 ; (7, embryo derived from inner 

 integument : *, inner integument ; o, outer integument ; x 246. After HEGELMAiER. 46 



at a loss to understand (Fig. 107). In the allied Helosis guaya- 

 nensis, also, Chodat and Bernard 64 think that fertilization does 

 not occur, and that the embryo arises apogamously from the 

 endosperm. 



It is evident that polyembryony is by no means so rare a 



