Black Radish- Names, Seeds, and Seedlings.

Black Radish scientific name is Raphanus sativus L. var. niger (Mill.) S. Kerner (Family Cruciferae [Brassicaceae]). Words "Round" and "Long" are used as a part of common name to escribe difference in the root shapes. The word "Spanish" is used in North America mainly. The following picture demonstrate difference in the root shape. Long roots seems to me derives from crosses with diakon that is closest relatives to black radish.


Picture Source:http://www.rustica.fr/articles-jardin/legumes-et-potager/radis-noir-radis-l-hiver,3144.html

 As an alternative name you can come across "Noir gros rond d'hiver". I think it is a name of old variety accepted as a common name. As far as this name I like to note the following. In the International Union for the Protection of New Varieties of Plants Black Radish Guidelines for the conduct of tests for distinctness, uniformity and stability "Noir gros rond d'hiver" name is used as the reference variety for some varietal characteristics. 
http://www.upov.int/edocs/mdocs/upov/en/tc_48/tg_63_7_proj_7_tg_64_7_proj_6.pdf

Although black radish is sold mainly as hereinloom varieties there is selection of varieties especially in the Eastern Europe. The most popular variety in Russia, for example,  is Грайворонская (Graivoronskaya). It is  late variety (about 110 days) with outstanding yield potential and resistant to bolting.

Due to significant difference in vegetation period and other varietal characteristics it is important to know your seed source. My seed source is from Oregon. In 2001 season it took 90 days to form apple size roots although per supplier label it matures in 60 days. 60 days gave me a quarter size roots only.

Germination trial in potting soil (100% emergence).