64 PRINGSHEIM, ON THE IMPREGNATION 



the bodies contained in the antlieridia and the spermatic 

 filaments in animals ; and again, in a few isolated observa- 

 tions on the sterility of female Mosses and RhizocarpecB in the 

 absence of the male plants or organs ; and lastly, in the 

 occurrence of hybrid forms among Ferns. All these phe- 

 nomena, allow the true nature of the antliei'idia to be assumed 

 with great probability, but they are insufficient to afford a 

 scientific proof of it. 



What has been wanting for a clear and convincing proof is 

 the demonstration of at least a single instance, in which the 

 entrance of the vegetable spermatozoids into the female organ, 

 and their influence thereupon may be seen with perfect dis- 

 tinctness and in a way readily at the command of any observer. 

 This requirement, however, is not fulfilled by our observations 

 with respect to the process in the sexual organs in either the 

 higher or the lower cryptogams. 



I do not deny the value of Thuret's researches, which show, 

 in the way of experiment, the sexuality of the FucacecB ; but 

 in morphological processes, direct visual observation of the 

 process is necessarily of greater value than experiments which 

 always leave room for some degree of doubt. Besides this, 

 Thuret has merely stated the results of his experiments, and 

 has not communicated the precise conditions under which 

 they were instituted. Experimental researches of this kind, 

 may, it is true, show the necessary existence of two kinds of 

 organs for the formation of the young plant, but they throw 

 no light upon the essential nature of the act of fertilization. 



I am equally disposed to recognize the value of Suminski's 

 statements, who says that he has witnessed the entrance of 

 the spermatozoids into the archegonium of Ferns, in Pteris 

 serrulata ; as well as the importance of Hofmeister's obser- 

 vation, who has noticed the same thing in Aspidium filix 

 mas. But in both these instances the tissue surrounding the 

 archegonium opposes such difficulties to precise observation, 

 and the phenomenon is so little under the control of the 

 inquirer, that the witnessing of this occurrence can only be 

 regarded as a rare piece of good fortune in an individual 

 observer. Such instances are, certainly, wholly unfitted to 

 constitute the basis of a general scientific conviction ; leaving 

 altogether out of question, the circumstance that Suminski's 

 observations have received much contradiction, and that, in 

 any case, he has been deceived as to the part played by the 

 spermatic filaments in the archegonium. 



It must, therefore, be regarded as a particularly fortunate 

 circumstance, that I have succeeded in witnessing the process 

 in a plant, in which it was possible to observe the penetration 



