Bearing in mind, then, the principle that _all_ cultivated hybrids should have a third part, cultivar-name, we can turn again to the use of the various possible designations for the second part listed above. The choice of designations depends, broadly speaking, on _convenience_, that is to say, on what, in practice, will be found the most useful method of referring to the plants concerned. In principle, of course, every hybrid whose parentage is known has an appropriate formula-designation, and in certain cases such a formula would be sufficient as a second part designation without inventing either a Latin name or a vernacular collective name. For instance, when there are only a very few forms of a particular cross, it might not be considered necessary to be able to refer to the forms collectively, and a second part name would not then be given. For example, _Rubus_ 'Merton Thornless,' when raised, was the only form of the hybrid _R. rusticanus inermis_ x _thyrsiger_ to be put into circulation, and it was not given a second part designation other than the appropriate formula. On the whole, however, it is usually desirable to have a second part, collective designation, rather than a formula only. Whether such designation should be a Latin name or a vernacular phrase, or both, depends on a number of factors which, as I have said, are not yet fully worked out or appreciated. Broadly speaking, if there are a large number of cultivars of a particular cross and these cultivars form a well-marked group, distinct from other hybrid groups in the genus, it is useful to have a vernacular designation for general use, _e.g._ 'Bellingham Hybrids' for all cultivars of the cross _Lilium Humboldtii_ x _pardalinum_. This purpose can, however, be equally well served by a Latin name, _e.g. Camellia_ x _Williamsii_ for all cultivars of the cross _C. japonica_ x _saluenensis_. Whichever method is chosen, two points are of great importance. Firstly, if a Latin name is given, it _must_ be accompanied by a Latin description. Secondly a vernacular designation _must_ contain some such word as Hybrids, Crosses, or the like, to distinguish it from a cultivar-name. The practice, in some groups, of giving "straight" cultivar-names as second part collective designations, followed by "var. so-and-so," is condemned by the Code. Existing names of this kind, however, can easily be brought into line by adding a word such as Hybrids or Grex to the old, second part, cultivar-name, and omitting the "var." thus, _Cattleya_ 'Fabia' var. 'Prince of Wales,' would become _C._ ('Fabia Grex') 'Prince of Wales' (Grex can he abbreviated to G. if desired). This alteration may seem over-pedantic, but if, in the naming of cultivated hybrids, a clear distinction is not kept between second and third part names, confusion, as I have pointed out, is likely to result.