[913] Gärtner, 'Bastarderzeugung,' s. 549. It is, however, doubtful whether these plants should be ranked as species or varieties.
[914] Gärtner, idem, s. 550.
[915] 'Journal de Physique,' tom. xxiii., 1783, p. 100. 'Act. Acad. St. Petersburgh,' 1781, part i. p. 249.
[916] 'Nouvelles Archives du Muséum,' tom. i. p. 49.
[917] L'Hermès, Jan. 14, 1837, quoted in Loudon's 'Gard. Mag.,' vol. xiii. p. 230.
[918] 'Comptes Rendus,' tom. xxxiv., 1852, p. 746.
[919] 'Géograph. Bot. de l'Europe,' tom. iii., 1854, p. 405; and 'De la Fécondation,' 1862, p. 302.
[920] 'Traité du Citrus,' 1811, p. 45.
[921] 'Transact. Linn. Soc.,' vol. ix. p. 268.
[922] Gärtner ('Bastarderzeugung,' s. 611) gives many references on this subject.