[427] Godron, 'De l'Espèce,' tom. ii. p. 106; Herbert on Crocus, in 'Journal of Hort. Soc.,' vol. i., 1846, p. 254.—Dr. Wight, from what he has seen in India, believes in this view; 'Madras Journal of Lit. and Science,' vol. iv., 1836, p. 61.
[428] Wahlenberg specifies eight species in this state on the Lapland Alps: see Appendix to Linnæus' 'Tour in Lapland,' translated by Sir J. E. Smith, vol. ii. pp. 274-280.
[429] 'Travels in North America,' Eng. translat., vol. iii. p. 175.
[430] With respect to the ivy and Acorus, see Dr. Bromfield in the 'Phytologist,' vol. iii. p. 376. See also Lindley and Vaucher on the Acorus.
[431] 'Annal. des Sc. Nat.,' 3rd series, Zool., tom. iv. p. 280. Prof. Decaisne refers also to analogous cases with mosses and lichens near Paris.
[432] Mr. Tuckerman, in Silliman's 'American Journal of Science,' vol. xlv. p. 41.
[433] Sir J. E. Smith, 'English Flora,' vol. i. p. 339.
[434] G. Planchon, 'Flora de Montpellier,' 1864, p. 20.
[435] On the non-production of seeds in England see Mr. Crocker, in 'Gardener's Weekly Magazine,' 1852, p. 70; Vaucher, 'Hist. Phys. Plantes d'Europe,' tom. i. p. 33; Lecoq, 'Géograph. Bot. de l'Europe,' tom. iv. p. 466; Dr. D. Clos, in 'Annal. des Sc. Nat.,' 3rd series, Bot., tom. xvii., 1852, p. 129: this latter author refers to other analogous cases. On the non-production of pollen by this Ranunculus see Chatin, in 'Comptes Rendus,' June 11th, 1866.
[436] 'Bastarderzeugung,' s. 565. Kölreuter ('Dritte Fortsetzung,' s. 73, 87, 119) also shows that when two species, one single and the other double, are crossed, the hybrids are apt to be extremely double.