210 Dr. L. Radlkofer 07i true Parthenogenesis in Plants. 



absence of pollen-tubes in the ovaries and ovules of Cannabis 

 and Mercurialis, — nor to institute here, as I did in that case, 

 comparative investigations on the development of the fecundated 

 and the virgin ova into embryos. I trust to be able to do so 

 hereafter. 



Reviewing the facts which compel us to transfer the idea of 

 Parthenogenesis in the vegetable kingdom from the domain of 

 chima^ras into the domain of reality, we find them, briefly, as 

 follows : — 



A. We are acquainted, in the specimens of Ccelehogyne culti- 

 vated in Europe, with plants in which the participation of the 

 pollen of the same plant in the production of the embryo is im- 

 possible. The participation of the pollen of any allied plant is 

 rendered in the highest degree improbable by the absence of all 

 signs of hybridation in the progeny. 



The absence of any such participation is directly demonstrated 

 here by microscopic investigation. 



This evidence is strengthened by the behaviour of the stigmas 

 of the ripening ovaries. Our observations on this point can of 

 course be only one-sided, but they are rendered good testimony 

 by the support derived from analogy. 



B. In other plants [Cannabis, Mercurialis) we may acknowledge, 

 not indeed the impossibility, but the great improbability of an 

 action of the pollen of the same or allied plants on flowering 

 female plants kept in closed chambers. 



For the absence of such action we are still without the nega- 

 tive proof, derived from microscopic examination, which we must 

 never dispense with in scientific questions. On the other liand, 

 we have a supplementary positive proof of it in the behaviour of 

 the stigmas, on which we here possess observations made on all 

 sides and mutually corrective. 



We might greatly increase the number of these cases of Par- 

 thenogenesis, if we made use of the statements for whose accuracy 

 we might take the name of the observers as surety. But we 

 prefer, in so important a question, in which is involved the 

 upsetting of a physiological law which is supposed to have been 

 just certainly established by the most recent researches, — not to 

 advance beyond our own observations; moreover, it was not 

 part of our plan to give a list of the cases in which Partheno- 

 genesis had been observed, but only a statement of those in 

 which and through which it could be demonstrated. 



Munich, Dec. 4, 1856. 



