Ocimum basilicum: Each basil variety has a unique set of chemical aromas that impart flavour. Native to wetter areas, basils don’t need “hairy” heat and drought shields like other herbs do, so leaves are almost bald. The small round structures are glands containing the chemicals that make basil’s flavours and aromas.
Rosmarinus officinalis: Rosemary’s piney flavour comes from chemicals made and stored in two structures: balloons (here, coloured yellow) and tiny toadstools (here, purple and white). Rosemary’s slightly furry feeling on the tongue comes from “hair” that helps the plant weather drought.
Lavandula spp.: Scattered among spiny hairs on lavender’s leaves, tiny balloons (yellow here) hold compounds that generate aroma as well as the flavour that lavender adds to foods and beverages. As with rosemary, the hairs on lavender leaves protect from sun glare and slow the evaporation of water.
Salvia officinalis: The leaf’s hairs evolved to accommodate the warm, dry climate where sage lives. The leaf’s glands (yellow balloons, some with pink) hold chemicals that help the plant defend against herbivores. Tear a sage leaf and you’ll smell a volatile fragrance being released from the small balloons of chemicals.