and its relativn to tltat in the Animal Kingdom. 445 



influence of tlic pollen-tube resides in its membrane, is no proof 

 that such is not the case ; but it is a sufficient reason for our 

 not introducing such a speculation here. We have not only a 

 right to assume the tranfifer of its contents into the germinal 

 vesicle in those cases where a direct contact of the pollen-tube 

 with the latter takes place, or only the membrane of the embryo- 

 sac intervenes, but we are compelled to assume it in the case 

 where, as the optical conditions alone suffice to show, the contents 

 on the two sides are different. 



des Sc. nat. 2 ser. xii. p. '6Cr2 (1839), translated from Allgemeine Garten- 

 zeitung, 1839, nos. 41 &42; also Meycn's Report on an Observation by 

 Ramiscb in Wiegnianu's Arcbiv, 5 Jabr. B. ii. ]). 42. Berlin, 1839). Tbe 

 more enigmatical tberefore appeared tbe uncontested fact of tbe formation 

 of seeds and embryos in tbe introduced female specimen of Calebogyne 

 ilicifolia (Eujiborbiaceae) witbout the presence of anthers. (Smith, Linn. 

 Trans, xviii. p. 509. London, 1841.) 



To the kindness of Sir William and of Dr. J. D. Hooker I am indebted 

 for materials for the investigation of this phsenomenon. Ccelehof/ytie, the 

 male spiked blossom of which is known in Europe only in the Ilookerian 

 Herbarium, is cultivated at Kew in company with a great number of other 

 Eupborbiaceae. The possibility of hybridation was tberefore considerable. 

 But this conjecture was necessarily greatly weakened by the observation, 

 that plants of the third and fourth generations still exactly resembled the 

 mother-plant. The circumstance that I detected a dry pollen-grain upon 

 the stigma of one of the fertile gcrmina which I examined, cannot, from 

 its isolated occurrence, counterbalance the evidence against hybridation 

 arising from the permanence of character. I could not discover a pollen- 

 tube in any part of an ovary or ovule of Calebogyne ; in other Euphor- 

 biacefc selected for comparative examination, there was no difficulty in 

 demonstrating a fragment of a pollen-tube protruding from tbe mamiila 

 nuclei. The young ovule of Calebogyne exhibited three germinal vesicles 

 adherent to the internal surface of its upper end ; in older ovaries, some- 

 times one, sometimes two, sometimes even all three, had been converted 

 into embryos. Tbe various conditions of development of the germinal 

 vesicle into the embryo exactly resembled those in all other Eupborbiaceae. 



Naudin has published an account of repeated and fully established 

 observations on the related cases in Mercurialis annua, Bryonia dioica. 

 Cannabis sativa, &c. (Bulletin de la Socic'te Botanique de France, xii. 

 p. 754 (no. 11, 1855), and more at length in the Comptes Rendus of the 

 present year). Liebmann also (Ann. Nat. Hist. 2 ser. vi. p. 395, 1850) 

 reports the formation of an embryo in a Cycad without the influence of 

 pollen. We may mention, finally, Gasparini's account (Note siir I'Origine 

 de I'Embryon. Ann. dcs Sc. nat. 3 ser. v. 1846, p. 306) of the formation 

 of embryos in Figs developed in summer, which are said never to contain 

 male flowers — although, from the actual words of this writer in a later 

 publication (Nouv. Recherch. sur I'Anat. et la Physiol, du Figuier. Ann. 

 des Sc. nat. 3 ser. xi. pp. 369, 371, 1849), it appears to follow that he 

 detected a pollen-tube in the micropyle-canal of the ovule of the Fig, but 

 mistook its nature. 



The cases in tbe Animal Kingdom comparable with these {Daphnia, &c.) 

 have already been mentioned, and we may direct attention on this head to 

 Siebold's recent essay on ' Parthenogenesis.' — Author's Note, Oct. 1856. 

 [See 'Annals,' the present volume, p. 204. — A. H.] 



