The naming of cultivars derived from crosses between two or more different species, belonging to the same or different genera, involves rather special problems. By "derived from" I mean not only the _first_ generation from a species cross, but all subsequent generations and back-crosses with the original parents or with members of the first or later generations. Any cultivar which is the progeny of a species cross, however remote, comes, for the purpose of the Code, under the heading of a hybrid and its naming is subject to definite rules. The full name of a "hybrid cultivar" must be regarded as consisting of three distinct parts: (1) the name of the genus (or "hybrid genus" if a hybrid between two or more genera is concerned); (2) a "collective" name or phrase covering _all_ the progeny resulting from the particular species-cross concerned; and (3) a cultivar-name for the particular form (cultivar) under consideration. In the name _Viburnum_ x _bodnantense_ 'Dawn,' _Viburnum_ is the generic name, x _bodnantense_ is the collective name for all progeny of the cross _V. fragans_ x _V. grandiflorum_, and 'Dawn' is the cultivar-name for a particular seedling of this parentage. It is essential always to bear in mind these three distinct parts of the name of a garden hybrid, even if, as it often done, one or other of the parts is omitted in actual usage; the three parts broadly correspond, of course, to the generic name, specific epithet, and cultivar-name of a non-hybrid cultivar (see above). Let us consider these three parts in turn and see what types of name can be used in each part in actual practice--and how this affects the naming of new "hybrid cultivars." The _first part_, the generic name, presents no difficulties, except in the case of new hybrids between two or more genera. Names of such "hybrid genera" are usually "manufactured" from a combination of the names of the parent genera (_e.g._ x _Heucherella_, from _Heuchera_ and _Tiarella_); in the case of hybrids between more than two genera, however, where a "combination" name would be unwieldy, it is permissible to make a new name by adding the termination _ara_ to the name of a person connected with the plant concerned (_e.g._ x _Sanderara_ for a tri-generic orchid hybrid). Before making a new "hybrid generic" name, a botanist should be consulted, as a Latin description in proper, botanical form must be provided. It will have been noticed that a multiplication sign is placed _in front of_ the names of "hybrid genera," but _after_ the generic name in the case of hybrids within a single genus; further details on this point are given later. The _second part_ of the full name of a hybrid is a more tricky business. It is, as I have said, a collective designation for all the progeny of the particular cross concerned, and it may take one or all of three possible forms:--