21S 



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 has not been observed in other 

 species of the genus. Hegelmaier exam- 

 ined A. fistulosum and J., 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 parthenogenetie 

 species of Alchemilla Murbeek 76 found 

 embryos from the egg, from the synergids, 

 and from the nueellar tissue (Fig. 106). 

 In Balanophora elongata and B. glo- 

 bosa fertilization is known not to occur, 

 and both Treub 46 and Lotsv 58 state that the embrvo 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; x 118.— After 

 Tretjakow. 38 



t o 



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 : x 15; B, tv o 

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

 enlarged and lying between the two embryos : x 24rt : C. embryo derived from inner 

 integument: /, inner integument ; o, outer integument; x 246. — After Hegelmaier. 15 



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 embrvo arises apogamously from the 

 endosperm. 



It is evident that polvembrvonv is bv no means so rare a 



