THE FERNS AND THEIR ALLIES n 



whole of the underside of the leaf is covered with 

 sporangia, and there is no indusium. 



3. Cyaiheacece. There are no British repre- 

 sentatives of this family, which is interesting, 

 owing to the fact that it includes the Tree Ferns. 



4. Gleicheniacea. A group of Ferns which 

 are almost entirely tropical. 



5. Schizceacecz. Another tropical family. 



6. Marattiacece. A family of large and hand- 

 some Ferns, the members of which occur in the 

 tropics. There are not many representatives of 

 this family nowadays, but remains in the Coal 

 Measures show that the species were very much 

 more numerous in Palaeozoic times. 



7. Osmundacece. A small family, but rather 

 an important one, owing to the fact that a lead- 

 ing representative, the Royal Fern (Osmunda 

 regalis), is so well known. In this species only 

 the upper portion of the leaf is fertile. The 

 sporangia have very shor+ stalks, and are not 

 provided with an annuku at all. They burst 

 open in a longitudinal slit, opposite to a special 

 group of cells just below the apex. The sorus 

 has no indusium. 



8. Ophioglossecz. This family is represented 

 by three British species, of which the Moonwort 

 (Botrychium lunaria) and the Adder's Tongue 

 (Ophioglosstim vulgatum) are best known. There 

 is much doubt as to whether this family can be 

 properly included amongst the Ferns at all. 

 We may here give them the benefit of the doubt. 

 The leaves in these species are unfolded from 

 the sides a totally distinct plan from that to 

 be observed in all the Ferns which have been 

 described, where the frond and its divisions are 

 unrolled upwards. The prothallus is a small 

 underground body destitute of chlorophyll. 

 The fertile leaves are distinguished from the 



