In plant morphology, thorns, spines, prickles, and in general spinose structures (as spinose teeth, spinose apical process) are all hard structures with sharp, stiff, ends, all of them with the same function of mechanically deterring herbivory. In common language the terms are used more or less interchangeably, but in botanical terms, thorns are derived from shoots (so they can be branched or not, they can have leaves or not, and they arise from a bud), spines are derived from leaves (the entire leaf or some part of the leaf that has vascular bundles inside, like the petiole or a stipule), and prickles are derived from the epidermis (so they can be found anywhere on the plant, and don't have vascular bundles inside so they can be removed more easily and cleany than thorns and spines). Leaf margins also may have teeth and if those teeth are sharp they are called spinose teeth, on a spinose leaf margin (some authors consider them a kind of spine). On a leaf apex, if there is an apical process (generally an extension of the midvein), and if it is specially sharp, stiff, and spinelike, it can be called spinose or pungent apical process (again, some authors call them a kind of spine) When epidermis is covered with very long, stiff trichomes (more correctly called bristles in this case, for some authors a kind of prickle) is called hispid vestiture, if is covered with stinging trichomes it can be called urent vestiture.
Types of spines. Cacti can have a particular kind of spine (modified leaf) very small and deciduous, with numerous retrorse barbs along its length, this particular spine is called glochidium (plural glochidia or glochids), as found in areoles of Opuntia. Spines can be petiolar spines as those of Foquieria, leaflet spines as in Phoenix, stipular spines as in Euphorbia, all those are examples of spines developing from a part of a leaf containing the petiole, midrib, or a secondary vein.
Nymphaea // is a genus of hardy and tender aquatic plants in the family Nymphaeaceae. The genus has a cosmopolitan distribution. Many species are cultivated as ornamental plants, and many cultivars have been bred. Some taxa occur as introduced species where they are not native, and some are weeds. Plants of the genus are known commonly as water-lilies, also styled water lilies and waterlilies. The genus name is from the Greek nymphaia and the Latin nymphaea, which mean "water-lily" and were inspired by the nymphs of Greek and Latin mythology.