Spectrophotometry inAllium ceparoot tip tissues showed that Feulgen mean absorption decreases in pericycle and protoderm cells from 500 to 1500 μ (starting from the distal end of the root cap), while in provascular cells it increases. These observations are probably consistent with the gradual accumulation of pericycle and protoderm cells in the G1phase of the mitotic cycle and with the ability of provascular cells to undergo chromosome endoreduplication.