222 Smooth-stemmed Form of Foxglove 



'purpurea-grandiflora (= -ambigua Murr.) hybrids which were found to 

 differ to a greater or less extent from the parent species in every par- 

 ticular: by Henslow^ in his detailed comparison of a spontaneously 

 occurring garden hybrid with its supposed parents purpurea and lutea : 

 and again in the still earlier account by Roth^ of the wild form media 

 presumed to be a hybrid between ambigua Murr. and lutea. In the case 

 of Digitalis certainly we should look too for some trace of that sterility 

 which is so marked a feature of indubitable species hybrids in this 

 genus^*. But we do not find either the one or the other. For except as 

 regards surface character the two forms nudicaidis and pubescens are 

 precisely similar, and both set seed abundantly. Moreover it is to be 

 noted that such spontaneously occurring forms as are judged to be of 

 hybrid origin exist for the most part in small numbers, only a single plant 

 perhaps being found wild or in a garden from time to time^ whereas, as 

 stated above, purpurea nudicaulis is not only of very general occurrence, 

 but where it occurs it is abundant. Furthermore, reference to other 

 species of Digitalis makes it evident that the nature of the differentiating 

 character in the present case cannot be taken as in itself necessarily 



1 Tram. Camb. Phil. 'Soc, Vol. iv. Part 2, 1831, p. 257. 



2 Cat. Bot. II. 1800. 



* Among mauy references to this fact since the early work of Koelreuter and Gartner 

 may be mentioned Focke's account of the following hybrids — purpurea-lutea, ambigua- 

 "purpurea, ambigua-nbscura, ambigua-lutea, ambigaa-lanata, ambigua-laevigata, laevigata- 

 lanata [Die Pjianzen-Mischliiige, 1881). In each case greateror less difficulty was experienced 

 ■ in obtaining the hybrid artificially, and the hybrids themselves proved in most cases to be 

 completely sterile. Of these various forms purpuri'a-lutea has been recorded from time to 

 time by various observers in the wild state. It was noticed by A. Saint-Hilaire and 

 de Salvert growing mixed with purpurea and lutea in a valley in the Auvergne district in 

 1808, and for several consecutive years the capsules were examined for seed, but each 

 season they were found to be shrivelled and to contain only aborted ovules (" Observations 

 sur la St^rilite des Hybrides," Mem Soc. d'hist. nat. Paris, i. 1823, p. 373). It is stated by 

 Wilson who raised a number of hybrids between these two species that the stamens were 

 often wanting, and that when present the pollen was found to be bad and he obtained no 

 seed (see Report of the third International Conference on Genetics, Roy. Hort. Soc, 1906). 



■* Among such cases may be instanced the single plant identified as D. piirpurascens 

 Roth, found by Le Jolis growing in the environs of Cherbourg amid plants of D. purpurea 

 (Ann. Sci. Nat., 3rd Ser. T. vii. 1847, p. 220) : the single specimen of D. longiflora noticed 

 by Lejeune near Verviers and regarded by him as answering closely to Koelreuter's hybrida 

 (Revue de la Flore des Environs de Spa, 1824, p. 126) : the single purpurea-lutea hybrid 

 described by Henslow which appeared in his garden among plants of the two parent species 

 (loc. cit.) : and other similar records to be found scattered through the literature of the 

 subject which emphasise the rarity of occurrence of these natural hybrids, their variability 

 of form, and the fact that when they arise they are often little durable (see Lamarck and 

 De CandoUe, Flore Fran^aise, Vol. vi. 1815, p. 412, and Vaucher, Histoire Physiologique des 

 Phintes d'Europe, T. iii. 1841, p. 520). 



