Although with viruses, the term species may not quite correspond to the way it is defined in biological systematics, it is perfectly reasonable and common to use it for viruses, too, since all viruses and viroids contain an original genome with a species-specific information. Its continuity over generations is guaranteed by replication in the host cells. Based on the shape of the virus particle, it is distinguished between rod-shaped and icosaedrical viruses with a capsid that seems almost spherical. Electron micrograph of a negatively stained specimen. The relief-like structure is a consequence of image processing.
Plant viruses have no specific mechanism for entering the host cell.
Cell wall and cuticle are difficult obstacles for them. The animal transmitter does in some cases also act as an intermediate host. This means that some plant viruses are able to multiply within animal tissue. Virus diseases of plants are relatively rare. Infection is scarcely strong enough to kill the plant.