Virus spread over plant tissue. (A) and (C) are screen-shots 75 hours post infection showing the number of virions, siRNAs and +RNA in the cells. (B) and (D) show the intracellular +RNA levels for a row of cells through time. (A) and (B) show results without silencing and (C) and (D) with silencing. Virions move from cell-to-cell, but siRNAs cannot spread.