The scientific classification of Pennywort and Crown-of-Thorns includes the entire classification chart that includes kingdom, family, clade, tribe etc. A kingdom is the second highest taxonomic rank. A taxonomic rank is the level that a living organisms are placed in hierarchical level of arrangement of life forms. All the living organisms are divided into kingdoms. Plant kingdom is a main classification of living organisms that include all plants. There are six kingdoms which are: Plantae, Animalia, Fungi, Protista, Aschaea/Archaeabacteria and Bacteria Eubacteria. Pennywort and Crown-of-Thorns kingdom and all other plants kingdom is Plantaea.
Plant family is the group of plants which have something in common. Pennywort and Crown-of-Thorns family is a major factor of Pennywort and Crown-of-Thorns Scientific Classification. Plant family helps you narrow the search of your plants. It also gives you idea about, how the plant looks, how the seed will be like etc. These two plant families can be different or same. Pennywort belongs to the family Apiaceae and Crown-of-Thorns belongs to the family Euphorbiaceae.
While comparing scientific classification, Pennywort and Crown-of-Thorns genus and other classification are also important. Also, when you compare Pennywort and Crown-of-Thorns, other factors should also be taken into considerations like order, subfamilies, tribe, clade etc. First plant's genus is Hydrocotyle and other plant's genus is Euphorbia. Pennywort tribe is Not Available and Crown-of-Thorns tribe is Euphorbieae. Pennywort clade is Angiosperms, Asterids and Eudicots and order is Apiales whereas Crown-of-Thorns clade is Angiosperms, Eudicots and Rosids and order is Euphorbiales. Every plant have subfamilies. Pennywort subfamilies are, Not Available and Crown-of-Thorns subfamilies are Euphorbioideae. In this way you can compare scientific classification of Pennywort and Crown-of-Thorns and other products also.