43 6 History of the Sexual Theory. [BOOK in. 



tion Schacht was soon after compelled to follow him, having be- 

 come acquainted with facts observed in the ovule of Gladiolus, 

 which were obviously irreconcilable with Schleiden's theory. 



Hofmeister had from the first directed special attention to 

 the questions, whether any bodies are found in the pollen-tube 

 which answer in any way to spermatozoids, and whether any 

 opening can be perceived at the end of the tube. He found 

 indeed forms in Coniferae in 1851, which reminded him of 

 the male organs of fertilisation in the higher Cryptogams ; but 

 the pollen-tube was closed both in them and in the rest of the 

 Phanerogams, in which moreover its outer coat attains to a 

 considerable thickness. There remained therefore only the 

 hypothesis, that a fluid substance passes through the walls of 

 the pollen-tube and of the embryo-sac and effects the fertilisa- 

 tion of the egg-cell ; thus it was not the theory of preformation 

 of the last century, to which Brongniart still adhered, but the 

 view represented by Koelreuter, which ultimately proved to be 

 nearer the truth, though it may be said that all that remained 

 of that view was, that the fertilising substance in the Phane- 

 rogams is a fluid. The granular contents of the pollen-grains, 

 which were supposed to be spermatozoids, have since been 

 partly found to be only innocent starch-grains and drops of oil. 



8. DISCOVERY OF SEXUALITY IN THE CRYPTOGAMS. 



1837-1860. 



BY the year 1845 no one capable of forming a judgment on 

 the question any longer doubted the existence of different 

 sexes in Phanerogams. But it was not so with the Cryptogams, 

 though a number of facts were acknowledged at this time 

 which seemed to point to the conclusion, that a moment 

 arrives sooner or later in the course of their development also, 

 when a sexual act is accomplished. But the question had not 

 as yet been systematically studied ; no experimental investi- 

 gations had been made, or observations of such a kind as to 

 demonstrate the necessity of sexual union. 



