104 THE KINGDOM OF MAN 



cryptogams or lower plants, including ferns, mosses, 

 and algae, was held to be that the latter produce 

 vibratile spermatozoa like those of animals which swim 

 in liquid and fertilise the motionless egg-cell of the 

 plant. Two Japanese botanists (and the origin of this 

 discovery from Japan, from the University of Tokio, 

 in itself marks an era in the history of science), Hirase 

 and Ikeno, astonished the botanical world fifteen years 

 ago by showing that motile antherozoids or spermatozoa 

 are produced by two gymnosperms, the ging-ko tree 

 (or Salisbury a) and the cycads (fig. 24). The pollen-tube, 

 which is the fertilising agent in all other phanerogams, 



FIG. 24. 



Spermatozoa (antherozoids) of Cycas revoluta, seen from the side and 

 from above. The spermatozoon is spherical, carrying a spiral band of 

 minute vibratile hairs (cilia) by which it is propelled. 



develops in these cone-bearing trees, beautiful motile sper- 

 matozoa, which swim in a cup of liquid provided for them 

 in connection with the ovules. Thus a great distinction 

 between phanerogams and cryptogams was broken down, 

 and the actual nature of the pollen-tube as a potential 

 parent of spermatozoids demonstrated. 



When we come to the results of the digging out 

 and study of extinct plants and animals, the most 

 remarkable results of all in regard to the affinities and 

 pedigree of organisms have been obtained. Among 

 plants the transition between cryptogams and phanero- 



