ovule is divided into two types based on the position of the sporogenous cell

Tenuinucellate type	Crassinucellate type
Sporogenous cell is hypodermal with a single layer of nucellar tissue around it.	Sporogenous cell is sub hypodermal
Have very small nucellus	Have fairly large nucellus.

Source	Contributed by the tapetum
Colour	Yellow or orange
Content	Carotenoids or flavonoids
Nature	Oily layer forming a thick viscous coating over pollen surface
Use	Attracts insects protects damage from UV radiation.

Supplies nutrition to the developing microspores contributes sporopollenin through, ubisch bodies. This plays an important role in pollen wall formation. The pollen kit material is contributed by tapetal cells, and is later, transferred to the pollen surface. Exine protein responsible for rejection reaction are derived from tapetal cells.

Endothecium is a single layer of radially elongated cells, The inner tangential wall of this cell develops bands of a cellulose, The cells are hygroscopic. The stomium of anther lobe lack these thickenings. Stomium along with the hygroscopic nature of endothecium helps in the dehiscence of anther

The primary endosperm nucleus divides immediately after fertilization. It develops into an endosperm which is a nutritive tissue and a regulatory structure. The zygote divides only after that to form an embryo so that it can get nourishment from the endosperm that has formed earlier.

Occurrence of more than one embryo in a seed is called polyembryony.
The seedlings formed from the nucellar tissue in citrus are found better clones for orchards. Embryos derived through polyembryony are found virus free.

In some species (unitegmic, tenuinucellate) the inner layer of integument becomes specialized, The layer is nutritive in function for the embryosac. This layer is called endothelium or integumentary tapetum.
Example:
Asteraceae.

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.