Orbicules are small, round structures found in the cells of various plants. They are usually composed of lipids and proteins and are thought to play a role in pollen development and dispersal. The discovery of orbicules is credited to Ubisch, making option B the correct answer.

Explanation:

Ubisch's Contribution:
- Emil Ubisch (1846-1926), a German botanist, is credited with the discovery of orbicules.
- In 1892, Ubisch observed the presence of small, round bodies in the tapetal cells of anthers, which are part of the male reproductive organs of plants.
- He named these structures "orbicules" due to their circular shape and reported his findings in a scientific paper.

Characteristics of Orbicules:
- Orbicules are found in the cytoplasm of certain plant cells, particularly in the tapetal cells of anthers and the sporopollenin-rich walls of pollen grains.
- They are usually small, ranging in size from a few micrometers to around 10 micrometers in diameter.
- Orbicules can vary in composition, but they are often composed of lipids, proteins, and sporopollenin, a polymer found in the walls of pollen grains.
- The exact function of orbicules is not fully understood, but they are thought to play a role in pollen development, especially in the formation of the pollen exine (outer wall).

Significance of Orbicules:
- Orbicules have been observed in a wide range of plant species, including both angiosperms (flowering plants) and gymnosperms (non-flowering plants like conifers).
- Their presence in the tapetal cells suggests a possible involvement in the synthesis and deposition of sporopollenin, a major component of the pollen wall.
- The sporopollenin layer provides protection to the pollen grain against desiccation, pathogens, and environmental stresses.
- Additionally, orbicules may also aid in the dispersal of pollen by providing a sticky or adhesive surface for pollen grains to attach to insects or other pollen vectors.

Conclusion:
- Orbicules were discovered by Emil Ubisch, a German botanist, in 1892.
- They are small, round structures found in certain plant cells, particularly in the tapetal cells of anthers and the walls of pollen grains.
- Orbicules are composed of lipids, proteins, and sporopollenin and are thought to play a role in pollen development and dispersal.