216 



MORPHOLOGY OF ANGIOSPERMS 



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

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

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

 rum, it lias not been observed in other 

 specie's of the genus. Hegelmaier 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 antipodals. In parthenogenetic 

 species of Alchemilla iMurbeck 76 found 

 embryos from the egg, from the synergids, 

 and from the nucellar tissue (Fig. 106). 

 In Bcdanophora elongata and B. glo- 

 hosa fertilization is known not to occur, 

 and both Treub* 8 and Lotsy 5S 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 



Fig. 104. — Allium odorum. 

 Three embryos derived 

 from the three antipo- 

 dal cells; < 116.— After 



TUKWilOU." 



A 



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 wall : s 15; i?, two 

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

 enlarged and lying between the two embryos ; x 24fi ; C\ embryo derived from inner 

 integument: 2, inner integument; 0, outer integument; x 24fi. — After Hegelmaier. 40 



at a loss to understand (Fig. 1<>7). In the allied Helosis guaya- 

 nensis, also, Cliodat and Bernard i;l 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 



