Any person who wilfully and unlawfully sets fire to any of the things following, that is to say—
(a) a crop of cultivated vegetable produce, whether standing or cut;
(b) a crop of hay or grass, whether the natural or indigenous product of the soil or not, and whether under cultivation or not, and whether standing or cut;
(c) any standing trees, saplings, or shrubs, whether indigenous or cultivated;
(d) any heath, gorse, furze, or fern;is guilty of a crime, and is liable to imprisonment for 14 years.