Many readers may be familiar with earlier codes, as that adopted by the American Pomological Society (which dates from 1847), that by the American Society of Agronomists (formulated in 1917-18), and with a third code adopted at the sessions of the Botanical Congress meeting in Cambridge, England, in 1935. Knowing of the provisions of these codes, you may ask, "What has the new one got that is different?" There are many new features of which the more significant are given below. Perhaps foremost is the recognition that, for the most part, the so-called varieties of garden plants are not uniform in their behavior. Some are nothing more than transplants of variations found in the wild, such as the Japanese _Juglans Sieboldiana_ var. _cordiformis_, a population having its own geographic range and distinguished from the typical element of the species by several morphological characters. It is a botanical variety that is cultivated. It is not a product of domestication. The code distinguishes from this botanical variety those so-called varieties that are the result of domestication, variants that have been produced in cultivation but are not known to occur and perpetuate themselves in the wild, such as Schwedler's maple known as _Acer Platanoides_ var. _Schwedleri_. Plants of this group, that may be grown from seed and which do show a limited variability, are distinguished from botanical varieties by placing them in a new category called cultivar (a name coined long ago by L. H. Bailey and meaning, a variety from cultivation). The abbreviation for the category is cv. Furthermore, in an effort to differentiate cultivar names from botanical names, it is provided that they be treated as are vernacular or fancy (common) names. That is, that the name be placed in single quotes and not italicized e.g., _Acer Platanoides_ cv. 'Schwedleri'. A third category is that of clone. A clone is an individual propagated not from seeds but by asexual means, as by grafting, budding, cuttings, etc. Most so-called varieties of nuts are clones. A clone may be selected from a species population, from a botanical variety, from a cultivar, or from anyone of several types of hybrid complexes. It may appear as a mutant of another clone. The name for it may, where there is need for precision, be attached to the name of the species (or hybrid) from which it was selected, as _Corylus Avellana_ cl. 'DuChilly' or reduced to _Corylus_ cl. 'DuChilly.' For the hybridizer naming and introducing new hybrids to cultivation, the Code is more helpful than any previous set of rules and the needs of hybridizers of various groups have been considered. Many examples illustrating application of each provision are given in the unabridged version.