Figure 4.

Anatomy of an R. acris petal. (a) Low-temperature scanning electron micrograph of a cut petal. The upper epidermis (arrow) is a flat layer with thickness of a few micrometres. Below the epidermis are the randomly distributed starch cells (asterisk). The size of the air spaces beneath the epidermis is variable and large air spaces exist between the starch cells and cells of the mesophyll layer. Scale bar: 10 µm. (b) Diagram of a Ranunculus petal; ue: upper epidermis; sl: starch layer; m: mesophyll; le: lower epidermis.