It is not considered necessary here to give a technical discussion of theof plants. It is, however, necessary and essential for the reader to have a general understanding of the meaning of such group names as family, tribe, genus, species, and variety.
The family includes those plants which have in common certain characteristics which the botanists consider indicate a definite, but in some cases rather distant, relationship; for instance, the rose and the apple belong to the same family, and it may be rather a shock to learn that the potato, the tomato, and the tobacco plant are all members of the same family.
There are members of thefamily which differ quite as widely from one another as these plants mentioned, and this equally applies to the other succulents; indeed, there are plants amongst the other succulents which look very much like , and it is very easy for the beginner to mistake these for true . However, with a little experience the beginner will soon be able to differentiate between the two.
The term tribe applies only to the family Cactaceae, which is divided into threeknown as tribes. The members of each tribe have not only the characteristics of the family but they have other characteristics which set them apart from the rest of the family. The tribes are divided into smaller , each known as a genus (plural genera).
Members of a genus resemble each other much more closely than do members of the family. Each species has additional characteristics common to all other members of the genus.
The genus is composed of groups of individuals des-ignated as species; that is, groups of individuals which resemble each other in all their constant characteristics.
Occasionally, a group of individuals within a species has one or more characters more or less persistent, but not important enough to warrant its consideration as a separate species. These individuals are known as varieties.
The classification of the other succulents is by family, sub-family, genus, species, and variety.
CLASSIFICATION TRIBE I
OPUNTIEAE Opuntia Nopalea, etc.
TRIBE III. CEREEAE
Sub-Tribe I. CEREANAE Cereus Monvillea Cephalocereus Espostoa Oreocereus Pachycereus Lemaireocereus Wilcoxia Nyctocereus Heliocereus Trichocereus Harrisia Cleistocactus Carnegiea Lophocereus, etc.
HYLOCEREANAE Hylocereus Selenicereus Aporocactus, etc.
Echinocereus Chamaecereus RebutiaMediolobivia Echinopsis, etc. THE CACTACEAE Sub-Tribe IV
Ariocarpus Obregonia Lophophora Aztekium Epithelantlia Hamatocactus Leuchtenbergia Stenocactus Ferocactus Echinomastus Gymnocalycium Echinocactus Astrophytum Notocactus Parodia, etc.
Sub-Tribe V. CACTANAE
Thelocactus CoryphanthaDolichothele, etc.
Erythrorhipsalis Rhipsalis, etc.