The aestivation of the calyx and corolla in 640 mature flower buds of Ranunculus repens from two sites near London is recorded.

Only two forms of quincuncial arrangement of the calyx are found and in almost equal numbers. One form is the mirror-image of the other and they continue the spiral from the prophylls in the left or right direction respectively.

All thirty-two possible arrangements of the corolla are found in both samples but their frequencies are very unequally distributed. There are more quincuncial and less apotactous and convolute forms than is expected by chance alone.

At the three posterior positions the two possible overlaps are more or less equally frequent overall, but there is a high correlation between the type of calyx and direction of the overlap. The predominating overlap is the eutopic one, i.e. the overlap at each position found in the corolla arrangement which continues the 2/5 spiral from the calyx. Overlaps involving the anterior petal appear to be entirely due to chance although in the site 1 sample there is a significant tendency to metatopy where the anterior and right lateral petals overlap.

These observations are compared with published work on aestivation in other species with variably imbricate pentamerous corollas and their significance is briefly discussed.