Brassica napus, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1964, Flora Europaea - Volume 1. Lycopodiaceae to Platanaceae, Cambridge University Press : 337

10. B. napus L. , Sp. Pl. 666 (1753).

Annual or biennial, with slender or stout, often fusiform or tuberous taproot; stems up to 150 cm. Basal leaves lyrate, sometimes ciliate, petiolate, glaucous and glabrous, or with few bristly hairs especially along veins; upper cauline leaves sessile, more or less entire, amplexicaul. Open flowers not overtopping buds of inflorescence. Sepals erecto-patent. Petals 10-18 mm, yellow. Siliqua 50-100x2-5- 4 mm, suberect, attenuate into a long slender beak 5-25(-30) mm. 2« = 38. Cultivated in most European countries and naturalized in many o f them. In addition to subsp. napus a large number of cultivars are extensively cultivated. There are numerous different classifications of these cultivars and interpretations of their relationship to the wild subspecies. A summary is given in E. N. Sinskaja, Bull. Appi. Bot. Pl.-Breed. (Leningrad) 33: 233-50(1960). The principal ones are the following which occasionally occur as escapes: subsp. pabularia (DC.) Janchen (‘primitive’ leaf rape), with a slender, annual root and crispate, dissected leaves, subsp. oleifera DC. (rape), biennial with a non-tuberous root, lyrate-pinnatifid leaves, and subsp. rapifera Metzger , biennial with a thickened, more or less globose, fleshy, edible stem-base and a taproot. Var. napobrassica (L.) Reichenb. (swede) (2n=38), with pale buff-coloured flowers and an edible swollen stem-base and yellow- fleshed taproot, has been derived from B. oleracea x B. napus by dibasic polyploidy. It is thought that crosses of B. oleracea subsp. oleracea (2/7= 18) with B. rapa (2« = 20) gave rise to subsp. pabularia (2« =38), from which subsp. napus (2/7 = 38) and subsp. rapifera (2n = 38) and other cultivars were derived.