V] POLLINATION AND FERTILISATION 75 



It is well to bear in mind that the event of 

 fertilisation is probably the most critical in the 

 whole life-story. There is no doubt that it figured 

 in an equally critical way throughout evolution, and 

 was a crisis in each completed life-cycle. 



It is then right and fitting that a premier place 

 should be given to the comparison of methods of 

 fertilisation in discussions on descent. At first sight 

 there may seem to be little relation between the 

 propagative method of a Flowering plant here 

 described and that of a Fern already detailed in 

 Chapter III. So long as the external features only 

 are noted the divergence appears to be a wide one. 

 It is only when the details are followed out that an 

 essential similarity appears. As a matter of fact an 

 adequate knowledge of the propagative process in 

 Ferns long preceded that of the corresponding events 

 in the Flowering plants. It remained for modern 

 methods of preparation to show how the nuclei 

 behave, and it is upon this that the whole comparison 

 turns. We now know that in the fertilisation of the 

 Fern, just as much as in that of the Flowering plant, 

 the essential point is the coalescence of two cells, 

 and especially of the nuclei of two cells, which are 

 more or less distinct in their origin. In the Fern 

 the spermatozoid conveying the male nucleus makes 

 its own way to tlie nucleated ovum. In the Flowering 

 plant the male gamete is non-motile and is handed 



