POLYEMBRYONY

 The phenomenon of the occurrence of more than one embryo is a seed is called as polyembryony .

It was first discovered by Antony Von Leekwenhock in 1719 in contain orange seeds.

According to Ernst 1918 and Schnarf 1929 polyembryony is classified into  2 types 

a- True polyembryony 

b- False polyembryony

In true polyembryony the extra embryos are developed from the same embryosac .

True polyembryony may be of following types 

1- Simple polyembryony - It occurs due to the fertilization of many eggs of a single embryosac.

Example - gretum 

2- Cleavage polyembryony - It occurs due to the cleavage of zygote or pro-embryo into two or more units which later develop into independent embryos .

Example - orchids , crotoloria , nicotiara rustica nymphaca advera

3- Polyembryony by the cells of embryosac 

The embryo may also develop from structure like synergids and antipodal cells in the embryosac .

Example -allium odorum, ulmus

4- Adventive polyembryony -In this type the embryo are formed the cells of nucellus or integuments .

Example - opuntia