FERTILISATION 



63 



species the process is more complicated : the germ tubes pro- 

 duced by the primary sporidia after conjugation give origin to 

 secondary sporidia ; these in turn produce germ tubes capable 

 of penetrating the tissues of the host and giving origin to rest- 

 ing spores." ^ Similar cases occur in Ustilago. 



Tulasne was rather sanguine when he wrote ^ that assiduous 

 observation, and the perfection \\\\\\ wliicli microscopes are 

 constructed will have enabled 

 the botanists of this age to 

 determine that there are no 

 really agamic plants — that is, 

 without sex. At any rate they 

 can from the present time sus- 

 pect with foundation that in 

 all vegetables, no matter to 

 what group they belong, there 

 exist two distinct orders of 

 reproductive organs, the rela- 

 tive values of which may be 

 compared to that of the two 

 sexes in animals. Until 

 latterly, however, tlie Lichens 

 and Fungi seemed to form ex- 

 ceptions to this rule, for all 

 the researches of phytologists could not discover in them that 

 duality of organs which, after having been for so long the 

 exclusive privilege of cotyledonous plants, has since been found 

 to belong to nearly all cryptogams. Experience and investiga- 

 tion of forty years have shown that Lichens and Fungi still 

 remain practically exceptions to the rule of sexuality. 



^ Massee, British Fungi — Phycomycetes, etc. (1891), p. 166. 

 ^ Comptes Rendus, vol. xxxv. (1852), p. 841. 



■TiUetia in germination. 

 De Bary. 



