THE EVIDENCE 75 



cells. Lastly, this particular kind of movement is 

 lost altogether; the more highly developed a plant 

 becomes, the less, generally speaking, is it like an 

 animal. 



The Cycadean method of fertilisation is par- 

 ticularly interesting because it is exactly inter- 

 mediate between the purely Cryptogamic process 

 in which everything depends on the active move- 

 ment of the spermatozoids, and the process in the 

 higher Seed-plants, in which the growth of the 

 pollen-tube is all important, the sperms being 

 carried as mere passengers to their destination. 

 In Cyads a pollen-tube is formed, and its growth 

 is so directed as to help the spermatozoids on 

 their way, but the final stage of their journey to 

 the egg-cell still has to be accomplished by their 

 own efforts. 



It is interesting to recall that the great Ger- 

 man botanist Hofmeister, fully forty years be- 

 fore the discoveries of Hirase and Ikeno, came 

 very near to predicting their results, for he said 

 that " impregnation in the Coniferse takes place 

 by a pollen-tube in the interior of which sper- 

 matozoa are probably formed." Though this is 

 not the case in the Coniferae generally, it has 

 proved to be true in Ginkgo (which was regarded 

 as a Conifer in Hofmeister's time), as well as in 

 the allied Cycads. 



In most Cycads only two spermatozoids are 



