Filiform apparatus are finger-like projections present at the micropylar end of synergids of embryo sac.

Filiform apparatus is a characteristic feature of the synergid cells of the female gametophyte (embryo sac) in angiosperms. The filiform apparatus is a structure that extends from the micropylar end of the synergid and penetrates between the cells of the pollen tube.

Function:
The filiform apparatus plays a crucial role in guiding the pollen tube towards the embryo sac during fertilization. It secretes a glycoprotein-rich material that acts as a chemoattractant for the pollen tube. This material is released into the micropylar canal, which is the entry point for the pollen tube to enter the embryo sac.

Structure:
The filiform apparatus is a finger-like projection that extends from the synergid cell into the micropylar canal. It is composed of cytoplasmic strands and is covered by a plasma membrane. The cytoplasmic strands are highly organized and arranged in a parallel manner.

Significance:
The filiform apparatus is a crucial structure in the process of double fertilization in angiosperms. It plays a vital role in guiding the pollen tube towards the embryo sac and facilitates the fusion of the male and female gametes.

In conclusion, the filiform apparatus is a characteristic feature of the synergid cells of the female gametophyte in angiosperms. It secretes a glycoprotein-rich material that acts as a chemoattractant for the pollen tube and is crucial in guiding the pollen tube towards the embryo sac during fertilization.

A synergid cell wall forms a highly thickened structure called the filiform apparatus at the micropylar end consisting of numerous finger like projections into synergid cytoplasm. These are necessary for pollen tube guidance in ovule. Thus called as a characteristic feature..