ORIGINAL COMMUNICATIONS. 



I. — Gartners Observations upon Muling among Plants. 

 By the Rev. M. J. Berkeley. 



(Second Notice; see Vol. V., p. 172.) 



In prosecuting experiments on muling', it becomes important to 

 inquire what is the efTect of alternating the sexes of the plants 

 under examination, making that species tlie subject of hybridiza- 

 tion which before supplied tlie male element. Tiie term cross- 

 ing, which is used by English authors in a very wide sense, is 

 confined to this especial plienomenon by Kolreuter and his 

 followers. Such experiments are by no means universally suc- 

 cessful ; but the point of interest is that, w here impregnation is 

 perfected, the resulting hybrid is in either case precisely the 

 same. Amongst a number of individuals a few slight variations 

 as to size and colour of the flowers or foliage may exist, but only 

 such as occur wherever a multitude of plants are raised imme- 

 diately from pure species. 



This result of cross-impregnation is the more remarkable, 

 since it is directly contrary to what takes place in the animal 

 kingdom, as the well-known crosses between the horse and ass 

 obviously prove. And not only so, but where many individuals 

 are the result of a single act of impregnation, as in the case of 

 the dog and wolf, there is by no means a constant type prevalent 

 through the whole litter. This difference is explicable by the 

 greater unity of type in plants, as regards sexuality, whether 

 absolutely coincident, as in the case of hermaphrodites, or 

 scarcely modified where the sexes are confined to distinct indi- 

 viduals. 



There are indeed a few cases amongst plants where the sexes 

 are separate, and the typical form different, as in Lychnis diurna 

 and vespertina ; but the mules derived from counter-impregna- 

 tion present no such striking differences as occur amongst ani- 

 mals, and slight variations of type under like circumstances 

 have been observed in the genus Digitalis. D. lanato-ochro- 

 leuca, for instance, has short large blossoms, with the upper lip 

 smaller and its margin waved : D. ochroleuco-lanata has a pro- 

 portionably longer, thinner, and more cylindrical blossom, with 

 a smaller distinctly three-toothed upper lip, and a sharp point 

 in the centre of the lower lip. Other examples might be brought 

 forward in the same genus. 



It is to be observed, however, that many futile attempts at 

 crossing in the genus Digitalis may be expected, though success 



VOL. VI. B 



