John Cancalosi / Cross-Section of Utah Septarian Nodule, Utah. A type of geode, Utah Septarian Nodules are found about 15 miles east of Zion National park. They were formed in an ancient sea floor during the Cretaceou...

Jouan Rius / Petrified wood segment, Blue Mesa Badlands, Petrified Forest National Park, Arizona, USA, December 2012.

Nigel Cattlin / Daisy (Bellis perennis) cross section, composite flower with white ray florets and yellow disk florets.

Nigel Cattlin / Dandelion (Taraxacum officinale), cross section of composite flower with disk and ray florets, on black background.

Nigel Cattlin / Spanish bluebell (Hyacinthoides hispanica) cross section of bulb with leaf and root development. Cultivated in garden. January.

Nigel Cattlin / Banana (Musa x paradisiaca) cross section showing tightly packed leaves is pseudostem.

Nigel Cattlin / Tulip (Tulipa sp) flower cross section with mature anthers and style, close up. Berkshire, England, UK. April.

Nigel Cattlin / Tulip (Tulipa sp) flower cross section with immature anthers and style, close up. Berkshire, England, UK. April.

Nigel Cattlin / Tulip (Tulipa sp) flower with red petals, cross section showing mature anthers and style. Berkshire, England, UK. April.

Nigel Cattlin / Tulip (Tulipa sp) flower with orange petals, cross section showing mature anthers and style. Berkshire, England, UK. April.

Nigel Cattlin / Broad bean (Vicia faba) young plant with early leaves and roots, uprooted and germinated seed split to show food reserve.

Nigel Cattlin / Broad bean (Vicia faba), close up of roots and cross section of germinated seed to show food reserve.