Vol. 7. No. 6. 



TORREYA 



June, 1907 

 NOTES ON POLYEMBRYONY 



By Melville T. Cook 



Polyembiyony has been reported as occurring in a large num- 

 ber of species. Braun * in i860 reported polyembryony as 

 known in twenty-one species, in thirteen genera, and in twelve 

 families. Since that time it has been reported in a number of 

 other species. The causes of this phenomenon are not thor- 

 oughly understood and are not always the same. Coulter and 

 Chamberlain t give six different methods by which two or more 

 embryos may be produced in a single seed and three forms of 

 pseudo-polyembryony as follows : 



True Polyembryony 



A. Embryos derived from cells outside the sac, hence sporo- 

 phytic tissue (vegetative multiplication or budding). 



1. Embryos derived from cells of the nucellus. 



2. Embryos derived from cells of the integument. 



B. Embryos derived from cells within the sac (parthenogenesis 

 and vegetative apogamy) ; although not in the same morpholog- 

 ical category, embryos from the suspensor are also included in 

 the list (vegetative multiplication or budding). 



1. Normal occurrence of two eggs. 



2. Embryos from synergids. 



3. Splitting of embryos derived from egg. 



4. Embryos from antipodal cells. 



5. Embryos from endosperm cells. 



6. Embryos from the suspensor. 



•■Braun, A. (Jeber Poiyembryonie und Keimungvon Caelebogyne, ein Nachtrag 

 zu der Abhandlung liber Parthenogenesis l)ei Pflanzen. Abhandl. Kongl. Akad 

 Wiss. Berlin 1859 : 109-263. i860. 



t Coulter and Chamberlain. Morphology of Angiosperms. 1903. 

 [Xo. 5 Vol. 7, of ToRREYA, comprising pages 89-II2, was issued May 20, 1907. 



113 



