208 Dr. L. Radlkofer o?i true Parthenogenesis in Plants, 



necessary for the development of the pollen-tubes from the pol- 

 len-grains, brings in its train the immediate death of the former, 

 and a destructive action upon the stigmas is usually ascribed to 

 the pollen-grains. In our Ccelebogijne, on the contrary, the stigma 

 not only does not wither and dry up at the epoch in which 

 the development of the embryo is announced by the expansion 

 of the ovary, but it grows and increases in size simultaneously 

 with the enlargement of the ovary. 



We are indeed deficient here in comparative observations on 

 the behaviour of the stigmas of individuals regularly exposed to 

 the influence of the pollen, which hitherto could only be ex- 

 amined in the native country of Coelebogyne ; and a doubt may 

 perhaps be expressed whether we may venture to take the per- 

 sistent enlargement of the stigmas of Ccelebogyne as a proof thfxi 

 no pollen has acted upon them, or whether we may not have to 

 do here with an exceptional peculiarity, opposed to the ordinary 

 behaviour of plants. For the removal of this doubt, however, 

 facts come to our aid from other quarters, facts which we have 

 become acquainted with through a series of observations on the 

 occurrence of Parthenogenesis in the vegetable kingdom, which 

 we place in a second rank, 



Spallanzani^s observation, of the power of reproduction pos- 

 sessed by the female plant of Hemp [Cannabis sativa), without 

 the cooperation of pollen, has been subjected, in the last few 

 years, by Ch. Naudin of Paris, to repeated test-experiments, the 

 investigations being extended at the same time to Mercurialis 

 annua and Bryonia dioica*. From all these plants he has ob- 

 tained fertile seeds, i. e. seeds containing an embryo, in spite of 

 the exclusion of the pollen. The plants raised from these, in 

 Cannabis, were male and female : no statement is made on this 

 point in reference to the other plants. 



With regard to the results obtained in Bryonia, we shall not 

 place any dependence upon them, since the specimens used in 

 the investigations were cultivated in the open ground, and there- 

 fore could not be guarded from the influence of the pollen with 

 all the precautions requisite in such experiments. 



The female Hemp-plants were, however, raised in a detached, 

 constantly closed chamber, so that the advent of pollen- grains, 

 either of the same or other species, was most improbable ; — I 

 will not say it was impossible, for I will not deny to accident 

 the pleasure of now and then intervening when we least expect 

 it, and since we even know that ordinary door- and window- 

 fittings can be no absolute obstacle to the entrance of pollen- 



* Bullet, de la Soc. Botan. de France, xii. p. 754, No. 11. Paris, 1855; 

 and Comptes Rendus, xliii. p. 538 (1856). 



