Exine	Intine
Thick outer layers	Thin inner layer
It is made of cellulose, sporopollenin, and pollenkitt	It is made up of pectin hemicellulose, cellulose, and callose
Ununiform layer	Uniform layer

Tapetum are of two types. Secretory tapetum and Invasive tapetum. Tapetum nourishes the pollen grains.

(a) Epidermis
(b) Endothecium
(c) Middle layers
(d) Tapetum

(a) Calyx
(b) Corolla
(c) Androecium
(d) Gynoecium

A single cell from a rare and endangered plant can be grown into a an entire plant. So it is considered as the best method.

Individuals formed by asexual reproductive methods are morphologically and genetically identical and are called clones.

The stem of a parent plant is allowed to develop roots. After formation of roots, the rooted part is cut and separated and planted to grow into a new plant (eg) Ixora and Jasminum.

Sucker - chrysanthemum
Stolon - jasmine

Hofmeister described the structure of pollen tetrad

Reproduction is a biological process in which an organism give rise to offsprings. This helps to maintain continuity of its species.

Mound Layering	Air Layering
A lower flexible branch of the plant is selected.	A healthy, stiff branch of the plant is selected.
The branch is bent to the ground.	The stem is girdled at the nodal region hormones applied.
A part of the branch is buried in the soil leaving the tips exposed and allowed for rooting	The girdled portion is covered with Damp or moist soil and allowed for rooting.

  Grafting Layering Types Types of grafting Bud/Approach/Tongue
Crown/Wedge Types of layering mound / Air Benefits More useful to get more varieties from a single Plant Can get only one type of offspring Usage More useful in horticultural filed Less useful technique in horticultural field Result Can get highly desirable characters from parent stock to different scion Can get same characteristics from parent to offspring

In Bryophyllum, the leaf is succulent and notched on its margin. Adventitious buds (epiphyllous buds) develop at these notches. They develop into new plants forming a root system. They become independent plants when the leaf gets decayed.

1824 - G.B. Amici discovered the pollentube.
1848 - Hofmeister described the structure of pollen tetrad.
1870 - Hanstein described the development of embryo in Capsella and Alisma.
1878 - E. Strasburger reported poly embryony.
1884 - E. Strasburger discovered the process of syngamy.
1898 & 1899 - S.G. Nawaschin and L. Guignard independently, discovered double fertilizations. 

Artificial propagation of higher plants used by man for a very long time are called conventional methods
1) Cutting
The cut parts from (root, stem, leaf) parent plant are grown in suitable medium. They grow into new plants
Example:
(i) Root Cutting - Malus.
(ii) Stem Cutting - Hibiscus.
(iii) Leaf cutting - Begonia.
2) Grafting
 Parts of two different plants are joined so that they continue to grow as one plant of the two plants the plant which is in contact with the soil is called stock the plant used for grafting is called scion.
Example:
(i) Citrus, Mango.
(ii) There are different types of grafting based on the method of uniting the scion and stock.
Layering
The stem of the parent plant is allowed to develop roots while still intact. After the roots formation rooted part is cut and planted to grow as a new plant.
Example:
Ixora, Jasminum
It is of two types - Mound / Air layering.