May, 1898.J 109 



ON THE POSITION 01^ THE ERUCTIEICATION IN 

 CERTAIN BRITISH FERNS AND HORSETAII^S. 



BY R. I.I.OYD PRAEGKR, B.E- 

 (Read before the Dublin Naturalists' Field Club, March 8th, 1898.) 



The Ferns and Horsetails are among the highest of the 

 Cryptogamia or " Flowerless Plants." They display an alter- 

 nation of generations. The sexual generation, or oophyte, 

 is a minute and short-lived plant. The asexual generation, 

 or sporophyte, is comparatively gigantic, usually lives for 

 several or many years, and this is that we call a F^ern or a 

 Horsetail, as the case may be. These higher cryptogams 

 have usuall}^ well- developed root, stem, and leaf, and on por- 

 tions of the stems or leaves is borne the fructification, that is, 

 the spores with their spore-cases and appendages. These 

 spores, when liberated from the spore-cases, and surrounded 

 by suitable conditions, germinate and produce again the 

 sexual generation or oophore. The position of the fructifica- 

 tion in the Ferns and Horsetails shows in different species a 

 good deal of variation. In most of our British Ferns it is 

 borne in small bundles on the back of the large and often 

 much-divided leaves or fronds ; in others of our Ferns only 

 on a certain portion of the fronds, or only on certain fronds. 

 In the Horsetails, it is borne sometimes at the top of the 

 simple or branched green stems, sometimes on stems set 

 apart for the purpose. L<et us look into this matter in greater 

 detail, considering not only the norm.al forms, but certain 

 abnormalities, some examples of which are figured, and tend 

 to throw interesting side-lights on the subject. 



We should expect to find the fructification borne in that 

 position which is most advantageous to the continued life of 

 the species — in other words, in the position which is best 

 suited for the proper ripening and dispersal of the spores. 

 The spores must be duly protected from cold and wet, and 

 at the same time they must be so borne that, when liberated, 

 they will be freely exposed to the wind, on which the plant 

 relies for their dispersal. These conditions we find duly 

 fulfilled. To take first the Ferns. In the sub-order Polypo- 

 diace<Cy to which almost all our British species belong, the spore- 

 cases are borne in clusters or sori oh the under side of the leafy 

 fronds. In the three species oi PolysticJmm (Shield Fern, Holly 



